diff --git a/codex-rs/Cargo.lock b/codex-rs/Cargo.lock
index 779785704..b843fcae6 100644
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -3770,6 +3770,7 @@ dependencies = [
  "codex-features",
  "codex-protocol",
  "codex-utils-absolute-path",
+ "codex-utils-cargo-bin",
  "codex-utils-output-truncation",
  "codex-utils-pty",
  "codex-utils-string",
diff --git a/codex-rs/tools/Cargo.toml b/codex-rs/tools/Cargo.toml
index 7d02f1bf3..7cc0e3484 100644
--- a/codex-rs/tools/Cargo.toml
+++ b/codex-rs/tools/Cargo.toml
@@ -31,6 +31,7 @@ tracing = { workspace = true }
 urlencoding = { workspace = true }
 
 [dev-dependencies]
+codex-utils-cargo-bin = { workspace = true }
 pretty_assertions = { workspace = true }
 
 [lib]
diff --git a/codex-rs/tools/tests/fixtures/json_schema_policy/google_calendar.json b/codex-rs/tools/tests/fixtures/json_schema_policy/google_calendar.json
new file mode 100644
index 000000000..9673ecf59
--- /dev/null
+++ b/codex-rs/tools/tests/fixtures/json_schema_policy/google_calendar.json
@@ -0,0 +1,85 @@
+{
+  "source": "standard/google_calendar/tools",
+  "tools": [
+    {
+      "name": "google_calendar_create_event",
+      "description": "Create a calendar event.",
+      "input_schema": {
+        "type": "object",
+        "properties": {
+          "event": {
+            "$ref": "#/definitions/Event"
+          },
+          "notify_attendees": {
+            "type": "boolean",
+            "description": "Whether attendees should receive notifications."
+          }
+        },
+        "required": [
+          "event"
+        ],
+        "definitions": {
+          "Event": {
+            "type": "object",
+            "description": "Calendar event payload.",
+            "properties": {
+              "title": {
+                "type": "string",
+                "description": "Event title."
+              },
+              "start": {
+                "anyOf": [
+                  {
+                    "$ref": "#/definitions/DateTime"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              }
+            }
+          },
+          "DateTime": {
+            "type": "object",
+            "description": "Calendar date-time.",
+            "properties": {
+              "dateTime": {
+                "type": "string",
+                "format": "date-time",
+                "description": "RFC3339 date-time."
+              },
+              "timeZone": {
+                "type": "string",
+                "enum": [
+                  "UTC",
+                  "America/Los_Angeles"
+                ],
+                "description": "IANA time zone."
+              }
+            }
+          },
+          "UnusedCalendarResource": {
+            "type": "string",
+            "description": "Unreachable calendar resource."
+          }
+        }
+      },
+      "expected_preserved": [
+        {
+          "pointer": "/properties/event/$ref",
+          "value": "#/definitions/Event"
+        },
+        {
+          "pointer": "/definitions/DateTime/properties/timeZone/enum/1",
+          "value": "America/Los_Angeles"
+        }
+      ],
+      "expected_pruned": [
+        "/definitions/UnusedCalendarResource"
+      ],
+      "expected_dropped_fields": [
+        "/definitions/DateTime/properties/dateTime/format"
+      ]
+    }
+  ]
+}
diff --git a/codex-rs/tools/tests/fixtures/json_schema_policy/google_drive.json b/codex-rs/tools/tests/fixtures/json_schema_policy/google_drive.json
new file mode 100644
index 000000000..bf37296cc
--- /dev/null
+++ b/codex-rs/tools/tests/fixtures/json_schema_policy/google_drive.json
@@ -0,0 +1,65 @@
+{
+  "source": "standard/google_drive/tools",
+  "tools": [
+    {
+      "name": "google_drive_copy_file",
+      "description": "Copy a Google Drive file.",
+      "input_schema": {
+        "type": "object",
+        "properties": {
+          "file": {
+            "description": "File selector.",
+            "oneOf": [
+              {
+                "type": "string",
+                "description": "A Drive file ID."
+              },
+              {
+                "type": "object",
+                "properties": {
+                  "shared_drive_id": {
+                    "type": "string",
+                    "description": "Shared drive identifier."
+                  }
+                }
+              }
+            ]
+          },
+          "metadata": {
+            "description": "Optional copy metadata.",
+            "allOf": [
+              {
+                "type": "object",
+                "description": "Base metadata.",
+                "properties": {
+                  "source": {
+                    "type": "string",
+                    "description": "Metadata source."
+                  }
+                }
+              }
+            ]
+          },
+          "title": {
+            "type": "string",
+            "description": "Copied file title."
+          }
+        },
+        "required": [
+          "file"
+        ]
+      },
+      "expected_preserved": [
+        {
+          "pointer": "/properties/title/description",
+          "value": "Copied file title."
+        }
+      ],
+      "expected_pruned": [],
+      "expected_dropped_fields": [
+        "/properties/file/oneOf",
+        "/properties/metadata/allOf"
+      ]
+    }
+  ]
+}
diff --git a/codex-rs/tools/tests/fixtures/json_schema_policy/microsoft_outlook_email.json b/codex-rs/tools/tests/fixtures/json_schema_policy/microsoft_outlook_email.json
new file mode 100644
index 000000000..bf0aff411
--- /dev/null
+++ b/codex-rs/tools/tests/fixtures/json_schema_policy/microsoft_outlook_email.json
@@ -0,0 +1,90 @@
+{
+  "source": "golden/microsoft_outlook_email/tools",
+  "tools": [
+    {
+      "name": "microsoft_outlook_email_send",
+      "description": "Send an Outlook email.",
+      "input_schema": {
+        "type": "object",
+        "properties": {
+          "message_id": {
+            "$ref": "#/$defs/Message/properties/id"
+          },
+          "attachment": {
+            "type": "array",
+            "items": {
+              "$ref": "#/$defs/Attachment"
+            }
+          }
+        },
+        "$defs": {
+          "Message": {
+            "type": "object",
+            "description": "Outlook message.",
+            "properties": {
+              "id": {
+                "type": "string",
+                "description": "Message identifier."
+              },
+              "sender": {
+                "$ref": "#/$defs/EmailAddress"
+              },
+              "importance": {
+                "type": "string",
+                "enum": [
+                  "low",
+                  "normal",
+                  "high"
+                ],
+                "description": "Message importance."
+              }
+            }
+          },
+          "Attachment": {
+            "type": "object",
+            "description": "Email attachment.",
+            "properties": {
+              "name": {
+                "type": "string",
+                "description": "Attachment file name."
+              }
+            }
+          },
+          "EmailAddress": {
+            "type": "object",
+            "description": "Email address object.",
+            "properties": {
+              "address": {
+                "type": "string",
+                "description": "SMTP address."
+              }
+            }
+          },
+          "GiantUnusedPayload": {
+            "type": "object",
+            "description": "Representative unreachable Outlook payload.",
+            "properties": {
+              "opaque": {
+                "type": "string"
+              }
+            }
+          }
+        }
+      },
+      "expected_preserved": [
+        {
+          "pointer": "/properties/message_id/$ref",
+          "value": "#/$defs/Message/properties/id"
+        },
+        {
+          "pointer": "/$defs/Message/properties/importance/enum/2",
+          "value": "high"
+        }
+      ],
+      "expected_pruned": [
+        "/$defs/GiantUnusedPayload"
+      ],
+      "expected_dropped_fields": []
+    }
+  ]
+}
diff --git a/codex-rs/tools/tests/fixtures/json_schema_policy/notion.json b/codex-rs/tools/tests/fixtures/json_schema_policy/notion.json
new file mode 100644
index 000000000..49a362d49
--- /dev/null
+++ b/codex-rs/tools/tests/fixtures/json_schema_policy/notion.json
@@ -0,0 +1,72 @@
+{
+  "source": "golden/notion/tools",
+  "tools": [
+    {
+      "name": "notion_fetch_page",
+      "description": "Fetch a Notion page.",
+      "input_schema": {
+        "type": "object",
+        "properties": {
+          "page": {
+            "$ref": "#/$defs/Page%20Ref"
+          },
+          "filter": {
+            "type": "object",
+            "additionalProperties": {
+              "$ref": "#/$defs/Filter"
+            }
+          },
+          "content_mode": {
+            "description": "How much content to return.",
+            "anyOf": [
+              {
+                "type": "string",
+                "enum": [
+                  "summary",
+                  "full"
+                ]
+              },
+              {
+                "type": "null"
+              }
+            ]
+          }
+        },
+        "$defs": {
+          "Page Ref": {
+            "type": "string",
+            "description": "Notion page ID or URL."
+          },
+          "Filter": {
+            "type": "object",
+            "description": "Filter object.",
+            "properties": {
+              "created_by": {
+                "type": "string",
+                "description": "Creator user ID."
+              }
+            }
+          },
+          "UnusedDatabase": {
+            "type": "object",
+            "description": "Unreachable Notion database schema."
+          }
+        }
+      },
+      "expected_preserved": [
+        {
+          "pointer": "/properties/page/$ref",
+          "value": "#/$defs/Page%20Ref"
+        },
+        {
+          "pointer": "/properties/content_mode/anyOf/0/enum/0",
+          "value": "summary"
+        }
+      ],
+      "expected_pruned": [
+        "/$defs/UnusedDatabase"
+      ],
+      "expected_dropped_fields": []
+    }
+  ]
+}
diff --git a/codex-rs/tools/tests/fixtures/json_schema_policy/oversized_notion_create_page_input_schema.json b/codex-rs/tools/tests/fixtures/json_schema_policy/oversized_notion_create_page_input_schema.json
new file mode 100644
index 000000000..b4957a183
--- /dev/null
+++ b/codex-rs/tools/tests/fixtures/json_schema_policy/oversized_notion_create_page_input_schema.json
@@ -0,0 +1,1124 @@
+{
+  "source": "golden/notion/tools",
+  "tools": [
+    {
+      "name": "create_page",
+      "description": "Create a Notion page.",
+      "input_schema": {
+        "$schema": "https://json-schema.org/draft/2020-12/schema",
+        "title": "create_page.input",
+        "type": "object",
+        "description": "Input schema for create_page.",
+        "$defs": {
+          "rich_text": {
+            "type": "object",
+            "description": "Notion rich text object. This schema captures the stable high-value fields and permits provider extensions.",
+            "properties": {
+              "type": {
+                "type": "string",
+                "description": "Rich text discriminator such as `text`, `mention`, or `equation`."
+              },
+              "plain_text": {
+                "type": "string",
+                "description": "Flattened plain-text representation."
+              },
+              "href": {
+                "type": [
+                  "string",
+                  "null"
+                ],
+                "description": "Optional hyperlink target when present."
+              },
+              "annotations": {
+                "type": "object",
+                "description": "Text annotations applied to this run.",
+                "properties": {
+                  "bold": {
+                    "type": "boolean"
+                  },
+                  "italic": {
+                    "type": "boolean"
+                  },
+                  "strikethrough": {
+                    "type": "boolean"
+                  },
+                  "underline": {
+                    "type": "boolean"
+                  },
+                  "code": {
+                    "type": "boolean"
+                  },
+                  "color": {
+                    "type": "string"
+                  }
+                },
+                "additionalProperties": true
+              },
+              "text": {
+                "type": "object",
+                "description": "Text payload for `type=text` entries.",
+                "properties": {
+                  "content": {
+                    "type": "string"
+                  },
+                  "link": {
+                    "anyOf": [
+                      {
+                        "type": "null"
+                      },
+                      {
+                        "type": "object",
+                        "properties": {
+                          "url": {
+                            "type": "string",
+                            "format": "uri"
+                          }
+                        },
+                        "required": [
+                          "url"
+                        ],
+                        "additionalProperties": false
+                      }
+                    ]
+                  }
+                },
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "icon": {
+            "type": "object",
+            "description": "Notion icon union. Keep provider variants explicit and allow future variants.",
+            "properties": {
+              "type": {
+                "type": "string",
+                "description": "Icon discriminator such as `emoji`, `external`, `file_upload`, `custom_emoji`, or `icon`."
+              },
+              "emoji": {
+                "type": "string",
+                "description": "Emoji character for `type=emoji`."
+              },
+              "name": {
+                "type": "string",
+                "description": "Named native icon or custom emoji name when applicable."
+              },
+              "color": {
+                "type": "string",
+                "description": "Optional icon color for native icon variants."
+              },
+              "external": {
+                "type": "object",
+                "properties": {
+                  "url": {
+                    "type": "string",
+                    "format": "uri"
+                  }
+                },
+                "additionalProperties": true
+              },
+              "file_upload": {
+                "type": "object",
+                "properties": {
+                  "id": {
+                    "type": "string"
+                  }
+                },
+                "additionalProperties": true
+              },
+              "custom_emoji": {
+                "type": "object",
+                "properties": {
+                  "id": {
+                    "type": "string"
+                  },
+                  "name": {
+                    "type": "string"
+                  },
+                  "url": {
+                    "type": "string",
+                    "format": "uri"
+                  }
+                },
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "file_ref": {
+            "type": "object",
+            "description": "Notion file union used by cover and attachments.",
+            "properties": {
+              "type": {
+                "type": "string",
+                "description": "File discriminator such as `external`, `file`, or `file_upload`."
+              },
+              "name": {
+                "type": "string"
+              },
+              "external": {
+                "type": "object",
+                "properties": {
+                  "url": {
+                    "type": "string",
+                    "format": "uri"
+                  }
+                },
+                "required": [
+                  "url"
+                ],
+                "additionalProperties": true
+              },
+              "file": {
+                "type": "object",
+                "properties": {
+                  "url": {
+                    "type": "string",
+                    "format": "uri"
+                  },
+                  "expiry_time": {
+                    "type": "string",
+                    "format": "date-time"
+                  }
+                },
+                "additionalProperties": true
+              },
+              "file_upload": {
+                "type": "object",
+                "properties": {
+                  "id": {
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "id"
+                ],
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "parent": {
+            "type": "object",
+            "description": "Notion parent reference. The exact allowed variants depend on the endpoint.",
+            "properties": {
+              "type": {
+                "type": "string",
+                "description": "Parent discriminator such as `page_id`, `data_source_id`, `database_id`, `block_id`, or `workspace`."
+              },
+              "page_id": {
+                "type": "string"
+              },
+              "data_source_id": {
+                "type": "string"
+              },
+              "database_id": {
+                "type": "string"
+              },
+              "block_id": {
+                "type": "string"
+              },
+              "workspace": {
+                "type": "boolean"
+              }
+            },
+            "required": [
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "date_value": {
+            "type": "object",
+            "properties": {
+              "start": {
+                "type": "string",
+                "description": "ISO 8601 date or datetime string."
+              },
+              "end": {
+                "type": [
+                  "string",
+                  "null"
+                ]
+              },
+              "time_zone": {
+                "type": [
+                  "string",
+                  "null"
+                ]
+              }
+            },
+            "required": [
+              "start"
+            ],
+            "additionalProperties": false
+          },
+          "user": {
+            "type": "object",
+            "description": "Notion user or bot object.",
+            "properties": {
+              "object": {
+                "type": "string",
+                "const": "user"
+              },
+              "id": {
+                "type": "string"
+              },
+              "name": {
+                "type": [
+                  "string",
+                  "null"
+                ]
+              },
+              "avatar_url": {
+                "type": [
+                  "string",
+                  "null"
+                ],
+                "format": "uri"
+              },
+              "type": {
+                "type": "string",
+                "enum": [
+                  "person",
+                  "bot"
+                ]
+              },
+              "person": {
+                "type": "object",
+                "properties": {
+                  "email": {
+                    "type": [
+                      "string",
+                      "null"
+                    ],
+                    "format": "email"
+                  }
+                },
+                "additionalProperties": true
+              },
+              "bot": {
+                "type": "object",
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "object",
+              "id",
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "property_value": {
+            "type": "object",
+            "description": "Provider-native page property value object. This schema captures common property families and leaves room for future Notion property variants.",
+            "properties": {
+              "type": {
+                "type": "string"
+              },
+              "title": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "rich_text": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "number": {
+                "type": [
+                  "number",
+                  "null"
+                ]
+              },
+              "checkbox": {
+                "type": "boolean"
+              },
+              "url": {
+                "type": [
+                  "string",
+                  "null"
+                ],
+                "format": "uri"
+              },
+              "email": {
+                "type": [
+                  "string",
+                  "null"
+                ],
+                "format": "email"
+              },
+              "phone_number": {
+                "type": [
+                  "string",
+                  "null"
+                ]
+              },
+              "date": {
+                "anyOf": [
+                  {
+                    "$ref": "#/$defs/date_value"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "select": {
+                "anyOf": [
+                  {
+                    "type": "null"
+                  },
+                  {
+                    "type": "object",
+                    "properties": {
+                      "id": {
+                        "type": "string"
+                      },
+                      "name": {
+                        "type": "string"
+                      },
+                      "color": {
+                        "type": "string"
+                      }
+                    },
+                    "additionalProperties": true
+                  }
+                ]
+              },
+              "status": {
+                "anyOf": [
+                  {
+                    "type": "null"
+                  },
+                  {
+                    "type": "object",
+                    "properties": {
+                      "id": {
+                        "type": "string"
+                      },
+                      "name": {
+                        "type": "string"
+                      },
+                      "color": {
+                        "type": "string"
+                      }
+                    },
+                    "additionalProperties": true
+                  }
+                ]
+              },
+              "multi_select": {
+                "type": "array",
+                "items": {
+                  "type": "object",
+                  "properties": {
+                    "id": {
+                      "type": "string"
+                    },
+                    "name": {
+                      "type": "string"
+                    },
+                    "color": {
+                      "type": "string"
+                    }
+                  },
+                  "additionalProperties": true
+                }
+              },
+              "people": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/user"
+                }
+              },
+              "relation": {
+                "type": "array",
+                "items": {
+                  "type": "object",
+                  "properties": {
+                    "id": {
+                      "type": "string"
+                    }
+                  },
+                  "required": [
+                    "id"
+                  ],
+                  "additionalProperties": false
+                }
+              },
+              "files": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/file_ref"
+                }
+              },
+              "created_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "last_edited_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "formula": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "rollup": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "verification": {
+                "type": "object",
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "page": {
+            "type": "object",
+            "description": "Notion page object, modeled as a practical schema-authoring subset.",
+            "properties": {
+              "object": {
+                "type": "string",
+                "const": "page"
+              },
+              "id": {
+                "type": "string"
+              },
+              "created_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "last_edited_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "created_by": {
+                "$ref": "#/$defs/user"
+              },
+              "last_edited_by": {
+                "$ref": "#/$defs/user"
+              },
+              "cover": {
+                "anyOf": [
+                  {
+                    "$ref": "#/$defs/file_ref"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "icon": {
+                "anyOf": [
+                  {
+                    "$ref": "#/$defs/icon"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "parent": {
+                "$ref": "#/$defs/parent"
+              },
+              "archived": {
+                "type": "boolean"
+              },
+              "in_trash": {
+                "type": "boolean"
+              },
+              "is_locked": {
+                "type": "boolean"
+              },
+              "url": {
+                "type": "string",
+                "format": "uri"
+              },
+              "properties": {
+                "type": "object",
+                "description": "Page property map keyed by property name.",
+                "additionalProperties": {
+                  "$ref": "#/$defs/property_value"
+                }
+              }
+            },
+            "required": [
+              "object",
+              "id",
+              "parent",
+              "properties"
+            ],
+            "additionalProperties": true
+          },
+          "text_block_payload": {
+            "type": "object",
+            "properties": {
+              "rich_text": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "color": {
+                "type": "string"
+              },
+              "children": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/block"
+                }
+              }
+            },
+            "additionalProperties": true
+          },
+          "block": {
+            "type": "object",
+            "description": "Notion block object. The schema preserves the top-level discriminator and important typed payload families while allowing future provider expansion.",
+            "properties": {
+              "object": {
+                "type": "string",
+                "const": "block"
+              },
+              "id": {
+                "type": "string"
+              },
+              "type": {
+                "type": "string"
+              },
+              "has_children": {
+                "type": "boolean"
+              },
+              "archived": {
+                "type": "boolean"
+              },
+              "in_trash": {
+                "type": "boolean"
+              },
+              "created_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "last_edited_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "created_by": {
+                "$ref": "#/$defs/user"
+              },
+              "last_edited_by": {
+                "$ref": "#/$defs/user"
+              },
+              "parent": {
+                "$ref": "#/$defs/parent"
+              },
+              "paragraph": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "heading_1": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "heading_2": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "heading_3": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "heading_4": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "bulleted_list_item": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "numbered_list_item": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "toggle": {
+                "$ref": "#/$defs/text_block_payload"
+              },
+              "to_do": {
+                "allOf": [
+                  {
+                    "$ref": "#/$defs/text_block_payload"
+                  },
+                  {
+                    "type": "object",
+                    "properties": {
+                      "checked": {
+                        "type": "boolean"
+                      }
+                    },
+                    "additionalProperties": true
+                  }
+                ]
+              },
+              "callout": {
+                "allOf": [
+                  {
+                    "$ref": "#/$defs/text_block_payload"
+                  },
+                  {
+                    "type": "object",
+                    "properties": {
+                      "icon": {
+                        "anyOf": [
+                          {
+                            "$ref": "#/$defs/icon"
+                          },
+                          {
+                            "type": "null"
+                          }
+                        ]
+                      }
+                    },
+                    "additionalProperties": true
+                  }
+                ]
+              },
+              "code": {
+                "type": "object",
+                "properties": {
+                  "rich_text": {
+                    "type": "array",
+                    "items": {
+                      "$ref": "#/$defs/rich_text"
+                    }
+                  },
+                  "caption": {
+                    "type": "array",
+                    "items": {
+                      "$ref": "#/$defs/rich_text"
+                    }
+                  },
+                  "language": {
+                    "type": "string"
+                  }
+                },
+                "additionalProperties": true
+              },
+              "image": {
+                "type": "object",
+                "properties": {
+                  "caption": {
+                    "type": "array",
+                    "items": {
+                      "$ref": "#/$defs/rich_text"
+                    }
+                  },
+                  "type": {
+                    "type": "string"
+                  },
+                  "file": {
+                    "$ref": "#/$defs/file_ref"
+                  },
+                  "external": {
+                    "type": "object",
+                    "properties": {
+                      "url": {
+                        "type": "string",
+                        "format": "uri"
+                      }
+                    },
+                    "additionalProperties": true
+                  }
+                },
+                "additionalProperties": true
+              },
+              "tab": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "meeting_notes": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "unsupported": {
+                "type": "object",
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "object",
+              "id",
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "property_schema": {
+            "type": "object",
+            "description": "Data source property schema entry.",
+            "properties": {
+              "id": {
+                "type": "string"
+              },
+              "name": {
+                "type": "string"
+              },
+              "description": {
+                "anyOf": [
+                  {
+                    "type": "null"
+                  },
+                  {
+                    "type": "array",
+                    "items": {
+                      "$ref": "#/$defs/rich_text"
+                    }
+                  }
+                ]
+              },
+              "type": {
+                "type": "string"
+              },
+              "number": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "select": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "multi_select": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "status": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "date": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "people": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "files": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "checkbox": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "url": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "email": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "phone_number": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "formula": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "relation": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "rollup": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "created_time": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "last_edited_time": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "created_by": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "last_edited_by": {
+                "type": "object",
+                "additionalProperties": true
+              },
+              "verification": {
+                "type": "object",
+                "additionalProperties": true
+              }
+            },
+            "required": [
+              "type"
+            ],
+            "additionalProperties": true
+          },
+          "data_source": {
+            "type": "object",
+            "description": "Notion data source object representing a table under a database.",
+            "properties": {
+              "object": {
+                "type": "string",
+                "const": "data_source"
+              },
+              "id": {
+                "type": "string"
+              },
+              "name": {
+                "type": [
+                  "string",
+                  "null"
+                ]
+              },
+              "title": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "icon": {
+                "anyOf": [
+                  {
+                    "$ref": "#/$defs/icon"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "parent": {
+                "$ref": "#/$defs/parent"
+              },
+              "url": {
+                "type": "string",
+                "format": "uri"
+              },
+              "properties": {
+                "type": "object",
+                "description": "Schema map keyed by property name or id.",
+                "additionalProperties": {
+                  "$ref": "#/$defs/property_schema"
+                }
+              },
+              "in_trash": {
+                "type": "boolean"
+              }
+            },
+            "required": [
+              "object",
+              "id",
+              "parent"
+            ],
+            "additionalProperties": true
+          },
+          "database": {
+            "type": "object",
+            "description": "Notion database container object.",
+            "properties": {
+              "object": {
+                "type": "string",
+                "const": "database"
+              },
+              "id": {
+                "type": "string"
+              },
+              "parent": {
+                "$ref": "#/$defs/parent"
+              },
+              "title": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "description": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "icon": {
+                "anyOf": [
+                  {
+                    "$ref": "#/$defs/icon"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "cover": {
+                "anyOf": [
+                  {
+                    "$ref": "#/$defs/file_ref"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "is_inline": {
+                "type": "boolean"
+              },
+              "is_locked": {
+                "type": "boolean"
+              },
+              "in_trash": {
+                "type": "boolean"
+              },
+              "url": {
+                "type": "string",
+                "format": "uri"
+              },
+              "data_sources": {
+                "type": "array",
+                "items": {
+                  "type": "object",
+                  "properties": {
+                    "id": {
+                      "type": "string"
+                    },
+                    "name": {
+                      "type": [
+                        "string",
+                        "null"
+                      ]
+                    }
+                  },
+                  "required": [
+                    "id"
+                  ],
+                  "additionalProperties": true
+                }
+              }
+            },
+            "required": [
+              "object",
+              "id",
+              "parent"
+            ],
+            "additionalProperties": true
+          },
+          "comment": {
+            "type": "object",
+            "description": "Notion comment object.",
+            "properties": {
+              "object": {
+                "type": "string",
+                "const": "comment"
+              },
+              "id": {
+                "type": "string"
+              },
+              "discussion_id": {
+                "type": "string"
+              },
+              "created_time": {
+                "type": "string",
+                "format": "date-time"
+              },
+              "last_edited_time": {
+                "type": [
+                  "string",
+                  "null"
+                ],
+                "format": "date-time"
+              },
+              "created_by": {
+                "$ref": "#/$defs/user"
+              },
+              "parent": {
+                "$ref": "#/$defs/parent"
+              },
+              "rich_text": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/rich_text"
+                }
+              },
+              "markdown": {
+                "type": "string"
+              },
+              "attachments": {
+                "type": "array",
+                "items": {
+                  "$ref": "#/$defs/file_ref"
+                }
+              }
+            },
+            "required": [
+              "object",
+              "id",
+              "discussion_id",
+              "created_by"
+            ],
+            "additionalProperties": true
+          }
+        },
+        "properties": {
+          "parent": {
+            "$ref": "#/$defs/parent",
+            "description": "Request body field. Parent reference controlling whether the page is standalone or a row under a data source."
+          },
+          "properties": {
+            "type": "object",
+            "description": "Request body field. Page property map keyed by property name. Values should follow the target data source schema when the parent is a data source.",
+            "additionalProperties": {
+              "$ref": "#/$defs/property_value"
+            }
+          },
+          "children": {
+            "type": "array",
+            "description": "Request body field. Initial child blocks. Prefer this structured provider-native content form over markdown when exact block structure matters.",
+            "items": {
+              "$ref": "#/$defs/block"
+            }
+          },
+          "icon": {
+            "$ref": "#/$defs/icon",
+            "description": "Request body field. Optional page icon."
+          },
+          "cover": {
+            "$ref": "#/$defs/file_ref",
+            "description": "Request body field. Optional page cover image/file reference."
+          },
+          "template": {
+            "type": "object",
+            "description": "Request body field. Optional template application settings. Template application may be asynchronous.",
+            "additionalProperties": true
+          },
+          "markdown": {
+            "type": "string",
+            "description": "Request body field. Optional provider-supported markdown body. Included because Notion supports it, but block children remain the preferred structural primitive in this package."
+          }
+        },
+        "additionalProperties": false,
+        "required": [
+          "parent",
+          "properties"
+        ],
+        "not": {
+          "required": [
+            "children",
+            "markdown"
+          ]
+        }
+      }
+    }
+  ]
+}
diff --git a/codex-rs/tools/tests/fixtures/json_schema_policy/slack.json b/codex-rs/tools/tests/fixtures/json_schema_policy/slack.json
new file mode 100644
index 000000000..7461da73d
--- /dev/null
+++ b/codex-rs/tools/tests/fixtures/json_schema_policy/slack.json
@@ -0,0 +1,75 @@
+{
+  "source": "standard/slack/tools",
+  "tools": [
+    {
+      "name": "slack_schedule_message",
+      "description": "Schedule a Slack message.",
+      "input_schema": {
+        "type": "object",
+        "properties": {
+          "channel_id": {
+            "type": "string",
+            "description": "Slack channel ID."
+          },
+          "message": {
+            "type": "string",
+            "description": "Message text."
+          },
+          "post_at": {
+            "type": "integer",
+            "description": "Unix timestamp for delivery."
+          },
+          "thread_ts": {
+            "description": "Optional parent thread timestamp.",
+            "anyOf": [
+              {
+                "$ref": "#/$defs/SlackTs"
+              },
+              {
+                "type": "null"
+              }
+            ]
+          }
+        },
+        "required": [
+          "channel_id",
+          "message",
+          "post_at"
+        ],
+        "additionalProperties": false,
+        "$defs": {
+          "SlackTs": {
+            "type": "string",
+            "description": "Slack timestamp string.",
+            "pattern": "^[0-9]+[.][0-9]+$"
+          },
+          "UnusedPayload": {
+            "type": "object",
+            "description": "Large unreachable Slack payload.",
+            "properties": {
+              "debug": {
+                "type": "string"
+              }
+            }
+          }
+        }
+      },
+      "expected_preserved": [
+        {
+          "pointer": "/properties/thread_ts/anyOf/0/$ref",
+          "value": "#/$defs/SlackTs"
+        },
+        {
+          "pointer": "/$defs/SlackTs/description",
+          "value": "Slack timestamp string."
+        }
+      ],
+      "expected_pruned": [
+        "/$defs/UnusedPayload"
+      ],
+      "expected_dropped_fields": [
+        "/$defs/SlackTs/pattern"
+      ]
+    }
+  ]
+}
diff --git a/codex-rs/tools/tests/json_schema_policy_fixtures.rs b/codex-rs/tools/tests/json_schema_policy_fixtures.rs
new file mode 100644
index 000000000..1e244ade1
--- /dev/null
+++ b/codex-rs/tools/tests/json_schema_policy_fixtures.rs
@@ -0,0 +1,224 @@
+use codex_tools::ToolName;
+use codex_tools::mcp_tool_to_responses_api_tool;
+use pretty_assertions::assert_eq;
+use serde::Deserialize;
+use serde::de::DeserializeOwned;
+use serde_json::Value;
+use serde_json::json;
+use std::fs;
+use std::sync::Arc;
+
+const FIXTURE_PATHS: [&str; 5] = [
+    "tests/fixtures/json_schema_policy/slack.json",
+    "tests/fixtures/json_schema_policy/google_calendar.json",
+    "tests/fixtures/json_schema_policy/google_drive.json",
+    "tests/fixtures/json_schema_policy/notion.json",
+    "tests/fixtures/json_schema_policy/microsoft_outlook_email.json",
+];
+const OVERSIZED_NOTION_CREATE_PAGE_SCHEMA_PATH: &str =
+    "tests/fixtures/json_schema_policy/oversized_notion_create_page_input_schema.json";
+
+#[derive(Debug, Deserialize)]
+struct FixtureFile {
+    source: String,
+    tools: Vec<FixtureTool>,
+}
+
+#[derive(Debug, Deserialize)]
+struct FixtureTool {
+    name: String,
+    description: String,
+    input_schema: Value,
+    #[serde(default)]
+    expected_preserved: Vec<ExpectedValue>,
+    #[serde(default)]
+    expected_pruned: Vec<String>,
+    #[serde(default)]
+    expected_dropped_fields: Vec<String>,
+}
+
+#[derive(Debug, Deserialize)]
+struct ExpectedValue {
+    pointer: String,
+    value: Value,
+}
+
+#[test]
+fn json_schema_policy_fixtures_convert_to_responses_tools() {
+    for fixture in FIXTURE_PATHS.into_iter().map(load_fixture::<FixtureFile>) {
+        for fixture_tool in &fixture.tools {
+            let responses_tool = convert_fixture_tool(&fixture, fixture_tool);
+            let parameters = serde_json::to_value(&responses_tool.parameters)
+                .expect("responses parameters should serialize");
+
+            let expected_fields = [
+                (
+                    "preserve the tool name",
+                    json!(fixture_tool.name),
+                    json!(responses_tool.name),
+                ),
+                (
+                    "preserve the tool description",
+                    json!(fixture_tool.description),
+                    json!(responses_tool.description),
+                ),
+                (
+                    "remain a strict:false tool",
+                    json!(false),
+                    json!(responses_tool.strict),
+                ),
+                (
+                    "produce object-shaped parameters",
+                    json!("object"),
+                    parameters.get("type").cloned().unwrap_or(Value::Null),
+                ),
+            ];
+
+            for (message, expected, actual) in expected_fields {
+                assert_eq!(actual, expected, "{} should {message}", fixture_tool.name);
+            }
+            assert!(
+                parameters.get("properties").is_some_and(Value::is_object),
+                "{} should produce a parameters.properties object",
+                fixture_tool.name
+            );
+
+            for expected in &fixture_tool.expected_preserved {
+                assert_eq!(
+                    parameters.pointer(&expected.pointer),
+                    Some(&expected.value),
+                    "{} should preserve {}",
+                    fixture_tool.name,
+                    expected.pointer
+                );
+            }
+
+            for pointer in &fixture_tool.expected_pruned {
+                assert!(
+                    parameters.pointer(pointer).is_none(),
+                    "{} should prune unreachable definition {pointer}",
+                    fixture_tool.name
+                );
+            }
+
+            for pointer in &fixture_tool.expected_dropped_fields {
+                assert!(
+                    fixture_tool.input_schema.pointer(pointer).is_some(),
+                    "{} fixture should contain expected dropped field {pointer}",
+                    fixture_tool.name
+                );
+                assert!(
+                    parameters.pointer(pointer).is_none(),
+                    "{} should drop field {pointer} after JsonSchema conversion",
+                    fixture_tool.name
+                );
+            }
+        }
+    }
+}
+
+#[test]
+fn json_schema_policy_oversized_golden_schema_triggers_compaction() {
+    let fixture: FixtureFile = load_fixture(OVERSIZED_NOTION_CREATE_PAGE_SCHEMA_PATH);
+    let fixture_tool = fixture
+        .tools
+        .first()
+        .expect("oversized fixture should contain a tool");
+    let input_bytes = compact_json_len(&fixture_tool.input_schema);
+
+    let responses_tool = convert_fixture_tool(&fixture, fixture_tool);
+    let parameters =
+        serde_json::to_value(&responses_tool.parameters).expect("responses parameters serialize");
+    let output_bytes = compact_json_len(&parameters);
+
+    assert!(
+        output_bytes < input_bytes,
+        "compaction should reduce schema size from {input_bytes} bytes"
+    );
+
+    let absent_pointers = [
+        ("/description", "drop root description"),
+        ("/properties/parent/description", "drop nested descriptions"),
+        (
+            "/$defs",
+            "drop root definitions after stripping descriptions is insufficient",
+        ),
+    ];
+    for (pointer, message) in absent_pointers {
+        assert!(
+            parameters.pointer(pointer).is_none(),
+            "oversized schema should {message}"
+        );
+    }
+
+    let expected_values = [
+        (
+            "/properties/parent",
+            json!({}),
+            "rewrite local refs before dropping root definitions",
+        ),
+        (
+            "/properties/children/items",
+            json!({}),
+            "rewrite nested local refs before dropping root definitions",
+        ),
+        (
+            "/properties/markdown/type",
+            json!("string"),
+            "retain top-level argument shape",
+        ),
+        (
+            "/properties/properties/type",
+            json!("object"),
+            "retain object argument shape",
+        ),
+    ];
+    for (pointer, expected, message) in expected_values {
+        assert_eq!(
+            parameters.pointer(pointer),
+            Some(&expected),
+            "oversized schema should {message}"
+        );
+    }
+}
+
+fn load_fixture<T: DeserializeOwned>(path: &str) -> T {
+    let path = codex_utils_cargo_bin::find_resource!(path)
+        .unwrap_or_else(|err| panic!("resolve fixture {path}: {err}"));
+    let fixture = fs::read_to_string(&path)
+        .unwrap_or_else(|err| panic!("read fixture {}: {err}", path.display()));
+    serde_json::from_str(&fixture)
+        .unwrap_or_else(|err| panic!("parse fixture {}: {err}", path.display()))
+}
+
+fn convert_fixture_tool(
+    fixture: &FixtureFile,
+    fixture_tool: &FixtureTool,
+) -> codex_tools::ResponsesApiTool {
+    let name = &fixture_tool.name;
+    let input_schema = fixture_tool
+        .input_schema
+        .as_object()
+        .unwrap_or_else(|| panic!("{name} input_schema should be an object"))
+        .clone();
+    let tool = rmcp::model::Tool {
+        name: name.to_string().into(),
+        title: None,
+        description: Some(fixture_tool.description.clone().into()),
+        input_schema: Arc::new(input_schema),
+        output_schema: None,
+        annotations: None,
+        execution: None,
+        icons: None,
+        meta: None,
+    };
+
+    mcp_tool_to_responses_api_tool(&ToolName::namespaced(&fixture.source, name), &tool)
+        .unwrap_or_else(|err| panic!("convert {name} from {}: {err}", fixture.source))
+}
+
+fn compact_json_len(value: &Value) -> usize {
+    serde_json::to_vec(value)
+        .unwrap_or_else(|err| panic!("serialize compact JSON: {err}"))
+        .len()
+}