[codex] Support ui visibility meta for tools (#24700)

## Summary

Adds support for the same ui.visibility metadata as resources

[spec](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/draft/apps.mdx#resource-discovery)

codex-rs/core/src/mcp_tool_exposure.rs

@@ -3,6 +3,7 @@ use std::collections::HashSet;
 use codex_features::Feature;
 use codex_mcp::CODEX_APPS_MCP_SERVER_NAME;
 use codex_mcp::ToolInfo as McpToolInfo;
+use codex_mcp::tool_is_model_visible;
 
 use crate::config::Config;
 use crate::connectors;
@@ -51,7 +52,9 @@ pub(crate) fn build_mcp_tool_exposure(
 fn filter_non_codex_apps_mcp_tools_only(mcp_tools: &[McpToolInfo]) -> Vec<McpToolInfo> {
     mcp_tools
         .iter()
-        .filter(|tool| tool.server_name != CODEX_APPS_MCP_SERVER_NAME)
+        .filter(|tool| {
+            tool.server_name != CODEX_APPS_MCP_SERVER_NAME && tool_is_model_visible(tool)
+        })
         .cloned()
         .collect()
 }
@@ -72,6 +75,9 @@ fn filter_codex_apps_mcp_tools(
             if tool.server_name != CODEX_APPS_MCP_SERVER_NAME {
                 return false;
             }
+            if !tool_is_model_visible(tool) {
+                return false;
+            }
             let Some(connector_id) = tool.connector_id.as_deref() else {
                 return false;
             };

codex-rs/core/src/mcp_tool_exposure_test.rs

@@ -7,6 +7,7 @@ use codex_mcp::ToolInfo;
 use codex_tools::ToolName;
 use pretty_assertions::assert_eq;
 use rmcp::model::JsonObject;
+use rmcp::model::Meta;
 use rmcp::model::Tool;
 
 use super::*;
@@ -80,6 +81,16 @@ fn tool_names(tools: &[ToolInfo]) -> HashSet<ToolName> {
         .collect()
 }
 
+fn with_visibility(mut tool: ToolInfo, visibility: &[&str]) -> ToolInfo {
+    tool.tool.meta = Some(Meta(
+        serde_json::json!({ "ui": { "visibility": visibility } })
+            .as_object()
+            .expect("metadata object")
+            .clone(),
+    ));
+    tool
+}
+
 #[tokio::test]
 async fn directly_exposes_small_effective_tool_sets() {
     let config = test_config().await;
@@ -93,6 +104,84 @@ async fn directly_exposes_small_effective_tool_sets() {
     assert!(exposure.deferred_tools.is_none());
 }
 
+#[tokio::test]
+async fn excludes_tools_hidden_from_model_exposure() {
+    let config = test_config().await;
+    let visible_tool = make_mcp_tool(
+        "rmcp",
+        "visible_tool",
+        "mcp__rmcp",
+        "visible_tool",
+        /*connector_id*/ None,
+        /*connector_name*/ None,
+    );
+    let hidden_tool = with_visibility(
+        make_mcp_tool(
+            "rmcp",
+            "hidden_tool",
+            "mcp__rmcp",
+            "hidden_tool",
+            /*connector_id*/ None,
+            /*connector_name*/ None,
+        ),
+        &["app"],
+    );
+    let empty_visibility_tool = with_visibility(
+        make_mcp_tool(
+            "rmcp",
+            "empty_visibility_tool",
+            "mcp__rmcp",
+            "empty_visibility_tool",
+            /*connector_id*/ None,
+            /*connector_name*/ None,
+        ),
+        &[],
+    );
+    let visible_app_tool = with_visibility(
+        make_mcp_tool(
+            CODEX_APPS_MCP_SERVER_NAME,
+            "calendar_read",
+            "mcp__codex_apps__calendar",
+            "read",
+            Some("calendar"),
+            Some("Calendar"),
+        ),
+        &["app", "model"],
+    );
+    let hidden_app_tool = with_visibility(
+        make_mcp_tool(
+            CODEX_APPS_MCP_SERVER_NAME,
+            "calendar_open",
+            "mcp__codex_apps__calendar",
+            "open",
+            Some("calendar"),
+            Some("Calendar"),
+        ),
+        &["app"],
+    );
+    let mcp_tools = vec![
+        visible_tool.clone(),
+        hidden_tool,
+        empty_visibility_tool,
+        visible_app_tool.clone(),
+        hidden_app_tool,
+    ];
+    let connectors = vec![make_connector("calendar", "Calendar")];
+
+    let exposure = build_mcp_tool_exposure(
+        &mcp_tools,
+        Some(connectors.as_slice()),
+        &config,
+        /*search_tool_enabled*/ false,
+    );
+
+    assert_eq!(
+        tool_names(&exposure.direct_tools),
+        tool_names(&[visible_tool, visible_app_tool])
+    );
+    assert!(exposure.deferred_tools.is_none());
+}
+
 #[tokio::test]
 async fn searches_large_effective_tool_sets() {
     let config = test_config().await;