fix(plugins) rm plugin descriptions (#23254)

## Summary
Removes Plugin descriptions from the dev message, since descriptions of
skills and MCPs cover the capabilities offered by the plugin.

## Testing
- [x] Updates unit tests

codex-rs/core/src/context/available_plugins_instructions.rs

@@ -40,27 +40,17 @@ impl ContextualUserFragment for AvailablePluginsInstructions {
     fn body(&self) -> String {
         let mut lines = vec![
             "## Plugins".to_string(),
-            "A plugin is a local bundle of skills, MCP servers, and apps. Below is the list of plugins that are enabled and available in this session.".to_string(),
-            "### Available plugins".to_string(),
+            "A plugin is a local bundle of skills, MCP servers, and apps.".to_string(),
         ];
 
-        lines.extend(
-            self.plugins
-                .iter()
-                .map(|plugin| match plugin.description.as_deref() {
-                    Some(description) => format!("- `{}`: {description}", plugin.display_name),
-                    None => format!("- `{}`", plugin.display_name),
-                }),
-        );
-
         lines.push("### How to use plugins".to_string());
         lines.push(
-            r###"- Discovery: The list above is the plugins available in this session.
-- Skill naming: If a plugin contributes skills, those skill entries are prefixed with `plugin_name:` in the Skills list.
+            r###"- Skill naming: If a plugin contributes skills, those skill entries are prefixed with `plugin_name:` in the Skills list.
+- MCP naming: Plugin-provided MCP tools keep standard MCP identifiers such as `mcp__server__tool`; use tool provenance to tell which plugin they come from.
 - Trigger rules: If the user explicitly names a plugin, prefer capabilities associated with that plugin for that turn.
 - Relationship to capabilities: Plugins are not invoked directly. Use their underlying skills, MCP tools, and app tools to help solve the task.
-- Preference: When a relevant plugin is available, prefer using capabilities associated with that plugin over standalone capabilities that provide similar functionality.
-- Missing/blocked: If the user requests a plugin that is not listed above, or the plugin does not have relevant callable capabilities for the task, say so briefly and continue with the best fallback."###
+- Relevance: Determine what a plugin can help with from explicit user mention or from the plugin-associated skills, MCP tools, and apps exposed elsewhere in this turn.
+- Missing/blocked: If the user requests a plugin that does not have relevant callable capabilities for the task, say so briefly and continue with the best fallback."###
                 .to_string(),
         );
 

codex-rs/core/src/plugins/render_tests.rs

@@ -7,7 +7,7 @@ fn render_plugins_section_returns_none_for_empty_plugins() {
 }
 
 #[test]
-fn render_plugins_section_includes_descriptions_and_skill_naming_guidance() {
+fn render_plugins_section_keeps_plugin_usage_guidance_without_listing_plugins() {
     let rendered = render_plugins_section(&[PluginCapabilitySummary {
         config_name: "sample@test".to_string(),
         display_name: "sample".to_string(),
@@ -17,7 +17,7 @@ fn render_plugins_section_includes_descriptions_and_skill_naming_guidance() {
     }])
     .expect("plugin section should render");
 
-    let expected = "<plugins_instructions>\n## Plugins\nA plugin is a local bundle of skills, MCP servers, and apps. Below is the list of plugins that are enabled and available in this session.\n### Available plugins\n- `sample`: inspect sample data\n### How to use plugins\n- Discovery: The list above is the plugins available in this session.\n- Skill naming: If a plugin contributes skills, those skill entries are prefixed with `plugin_name:` in the Skills list.\n- Trigger rules: If the user explicitly names a plugin, prefer capabilities associated with that plugin for that turn.\n- Relationship to capabilities: Plugins are not invoked directly. Use their underlying skills, MCP tools, and app tools to help solve the task.\n- Preference: When a relevant plugin is available, prefer using capabilities associated with that plugin over standalone capabilities that provide similar functionality.\n- Missing/blocked: If the user requests a plugin that is not listed above, or the plugin does not have relevant callable capabilities for the task, say so briefly and continue with the best fallback.\n</plugins_instructions>";
+    let expected = "<plugins_instructions>\n## Plugins\nA plugin is a local bundle of skills, MCP servers, and apps.\n### How to use plugins\n- Skill naming: If a plugin contributes skills, those skill entries are prefixed with `plugin_name:` in the Skills list.\n- MCP naming: Plugin-provided MCP tools keep standard MCP identifiers such as `mcp__server__tool`; use tool provenance to tell which plugin they come from.\n- Trigger rules: If the user explicitly names a plugin, prefer capabilities associated with that plugin for that turn.\n- Relationship to capabilities: Plugins are not invoked directly. Use their underlying skills, MCP tools, and app tools to help solve the task.\n- Relevance: Determine what a plugin can help with from explicit user mention or from the plugin-associated skills, MCP tools, and apps exposed elsewhere in this turn.\n- Missing/blocked: If the user requests a plugin that does not have relevant callable capabilities for the task, say so briefly and continue with the best fallback.\n</plugins_instructions>";
 
     assert_eq!(rendered, expected);
 }

codex-rs/core/tests/suite/plugins.rs

@@ -210,12 +210,8 @@ async fn capability_sections_render_in_developer_message_in_order() -> Result<()
         "expected Apps -> Skills -> Plugins order: {developer_messages:?}"
     );
     assert!(
-        developer_text.contains("`sample`"),
-        "expected enabled plugin name in developer message: {developer_messages:?}"
-    );
-    assert!(
-        developer_text.contains("`sample`: inspect sample data"),
-        "expected plugin description in developer message: {developer_messages:?}"
+        !developer_text.contains("`sample`: inspect sample data"),
+        "did not expect plugin description in developer message: {developer_messages:?}"
     );
     assert!(
         developer_text.contains("skill entries are prefixed with `plugin_name:`"),