Split plugin install discovery into list and request tools (#23372)

## Summary
- Add `list_available_plugins_to_install` as the inventory step for
plugin and connector install suggestions.
- Slim `request_plugin_install` so it only handles the actual
elicitation, instead of carrying the full discoverable list in its
prompt.
- Emit send-time telemetry when an install elicitation is dispatched,
including requested tool identity in the event payload.
- Emit install-result telemetry through `SessionTelemetry`, including
tool type, user response action, and completion status.
- Update registration and tests to cover the new two-step flow while
keeping the existing `tool_suggest` feature gate unchanged.

## Testing
- `just fmt`
- `cargo test -p codex-tools`
- `cargo test -p codex-core request_plugin_install`
- `cargo test -p codex-core list_available_plugins_to_install`
- `cargo test -p codex-core
install_suggestion_tools_can_be_registered_without_search_tool`
- `cargo test -p codex-otel
manager_records_plugin_install_suggestion_metric`
- `cargo test -p codex-otel
manager_records_plugin_install_elicitation_sent_metric`
- `just fix -p codex-core`
- `just fix -p codex-tools`
- `just fix -p codex-otel`
- `cargo check -p codex-core`

codex-rs/core/src/session/mcp.rs

@@ -5,6 +5,7 @@ use codex_mcp::ElicitationReviewerHandle;
 use codex_protocol::config_types::ApprovalsReviewer;
 use codex_protocol::mcp_approval_meta::APPROVAL_KIND_KEY as MCP_ELICITATION_APPROVAL_KIND_KEY;
 use codex_protocol::mcp_approval_meta::APPROVAL_KIND_MCP_TOOL_CALL as MCP_ELICITATION_APPROVAL_KIND_MCP_TOOL_CALL;
+use codex_protocol::mcp_approval_meta::APPROVAL_KIND_TOOL_SUGGESTION as MCP_ELICITATION_APPROVAL_KIND_TOOL_SUGGESTION;
 use codex_protocol::mcp_approval_meta::APPROVALS_REVIEWER_KEY as MCP_ELICITATION_APPROVALS_REVIEWER_KEY;
 use codex_protocol::mcp_approval_meta::CONNECTOR_DESCRIPTION_KEY as MCP_ELICITATION_CONNECTOR_DESCRIPTION_KEY;
 use codex_protocol::mcp_approval_meta::CONNECTOR_ID_KEY as MCP_ELICITATION_CONNECTOR_ID_KEY;
@@ -21,6 +22,10 @@ use rmcp::model::Meta;
 use serde_json::Map;
 
 const MCP_ELICITATION_DECLINE_MESSAGE_KEY: &str = "message";
+const TOOL_SUGGESTION_ACTION_INSTALL: &str = "install";
+const TOOL_SUGGESTION_ACTION_KEY: &str = "suggest_type";
+const TOOL_SUGGESTION_TOOL_ID_KEY: &str = "tool_id";
+const TOOL_SUGGESTION_TOOL_TYPE_KEY: &str = "tool_type";
 
 #[derive(Debug, PartialEq)]
 enum GuardianElicitationReview {
@@ -33,6 +38,18 @@ struct GuardianMcpElicitationReviewer {
     session: std::sync::Weak<Session>,
 }
 
+pub(crate) struct McpServerElicitationOutcome {
+    pub(crate) response: Option<ElicitationResponse>,
+    pub(crate) sent: bool,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+struct PluginInstallElicitationTelemetryMetadata {
+    tool_type: String,
+    tool_id: String,
+    tool_name: String,
+}
+
 impl GuardianMcpElicitationReviewer {
     fn new(session: &Arc<Session>) -> Self {
         Self {
@@ -70,7 +87,7 @@ impl Session {
         turn_context: &TurnContext,
         request_id: RequestId,
         params: McpServerElicitationRequestParams,
-    ) -> Option<ElicitationResponse> {
+    ) -> McpServerElicitationOutcome {
         if self
             .services
             .mcp_connection_manager
@@ -78,11 +95,14 @@ impl Session {
             .await
             .elicitations_auto_deny()
         {
-            return Some(ElicitationResponse {
-                action: codex_rmcp_client::ElicitationAction::Accept,
-                content: Some(serde_json::json!({})),
-                meta: None,
-            });
+            return McpServerElicitationOutcome {
+                response: Some(ElicitationResponse {
+                    action: codex_rmcp_client::ElicitationAction::Accept,
+                    content: Some(serde_json::json!({})),
+                    meta: None,
+                }),
+                sent: false,
+            };
         }
 
         let server_name = params.server_name.clone();
@@ -98,7 +118,10 @@ impl Session {
                         warn!(
                             "failed to serialize MCP elicitation schema for server_name: {server_name}, request_id: {request_id}: {err:#}"
                         );
-                        return None;
+                        return McpServerElicitationOutcome {
+                            response: None,
+                            sent: false,
+                        };
                     }
                 };
                 codex_protocol::approvals::ElicitationRequest::Form {
@@ -154,11 +177,24 @@ impl Session {
             id,
             request,
         });
+        let plugin_install_telemetry = plugin_install_elicitation_telemetry_metadata(&event);
         turn_context
             .turn_metadata_state
             .mark_user_input_requested_during_turn();
         self.send_event(turn_context, event).await;
-        rx_response.await.ok()
+        if let Some(plugin_install_telemetry) = plugin_install_telemetry {
+            turn_context
+                .session_telemetry
+                .record_plugin_install_elicitation_sent(
+                    plugin_install_telemetry.tool_type.as_str(),
+                    plugin_install_telemetry.tool_id.as_str(),
+                    plugin_install_telemetry.tool_name.as_str(),
+                );
+        }
+        McpServerElicitationOutcome {
+            response: rx_response.await.ok(),
+            sent: true,
+        }
     }
 
     #[expect(
@@ -551,6 +587,33 @@ fn metadata_owned_string(meta: &Map<String, Value>, key: &str) -> Option<String>
         .map(ToOwned::to_owned)
 }
 
+fn plugin_install_elicitation_telemetry_metadata(
+    event: &EventMsg,
+) -> Option<PluginInstallElicitationTelemetryMetadata> {
+    let EventMsg::ElicitationRequest(ElicitationRequestEvent { request, .. }) = event else {
+        return None;
+    };
+    let codex_protocol::approvals::ElicitationRequest::Form {
+        meta: Some(Value::Object(meta)),
+        ..
+    } = request
+    else {
+        return None;
+    };
+    if metadata_str(meta, MCP_ELICITATION_APPROVAL_KIND_KEY)
+        != Some(MCP_ELICITATION_APPROVAL_KIND_TOOL_SUGGESTION)
+        || metadata_str(meta, TOOL_SUGGESTION_ACTION_KEY) != Some(TOOL_SUGGESTION_ACTION_INSTALL)
+    {
+        return None;
+    }
+
+    Some(PluginInstallElicitationTelemetryMetadata {
+        tool_type: metadata_owned_string(meta, TOOL_SUGGESTION_TOOL_TYPE_KEY)?,
+        tool_id: metadata_owned_string(meta, TOOL_SUGGESTION_TOOL_ID_KEY)?,
+        tool_name: metadata_owned_string(meta, MCP_ELICITATION_TOOL_NAME_KEY)?,
+    })
+}
+
 fn mcp_elicitation_request_id(id: &RequestId) -> String {
     match id {
         rmcp::model::NumberOrString::String(value) => value.to_string(),

codex-rs/core/src/session/mcp_tests.rs

@@ -96,6 +96,63 @@ fn guardian_elicitation_review_request_defaults_missing_tool_params() {
     assert_eq!(arguments, Some(json!({})));
 }
 
+#[test]
+fn plugin_install_elicitation_telemetry_metadata_requires_install_tool_suggestion() {
+    let event = EventMsg::ElicitationRequest(ElicitationRequestEvent {
+        turn_id: Some("turn-1".to_string()),
+        server_name: "codex_apps".to_string(),
+        id: codex_protocol::mcp::RequestId::String("request-1".to_string()),
+        request: codex_protocol::approvals::ElicitationRequest::Form {
+            meta: Some(json!({
+                "codex_approval_kind": "tool_suggestion",
+                "suggest_type": "install",
+                "tool_type": "plugin",
+                "tool_id": "slack@openai-curated",
+                "tool_name": "Slack",
+            })),
+            message: "Install Slack?".to_string(),
+            requested_schema: json!({
+                "type": "object",
+                "properties": {},
+            }),
+        },
+    });
+
+    assert_eq!(
+        plugin_install_elicitation_telemetry_metadata(&event),
+        Some(PluginInstallElicitationTelemetryMetadata {
+            tool_type: "plugin".to_string(),
+            tool_id: "slack@openai-curated".to_string(),
+            tool_name: "Slack".to_string(),
+        })
+    );
+
+    let enable_event = EventMsg::ElicitationRequest(ElicitationRequestEvent {
+        turn_id: Some("turn-1".to_string()),
+        server_name: "codex_apps".to_string(),
+        id: codex_protocol::mcp::RequestId::String("request-2".to_string()),
+        request: codex_protocol::approvals::ElicitationRequest::Form {
+            meta: Some(json!({
+                "codex_approval_kind": "tool_suggestion",
+                "suggest_type": "enable",
+                "tool_type": "plugin",
+                "tool_id": "slack@openai-curated",
+                "tool_name": "Slack",
+            })),
+            message: "Enable Slack?".to_string(),
+            requested_schema: json!({
+                "type": "object",
+                "properties": {},
+            }),
+        },
+    });
+
+    assert_eq!(
+        plugin_install_elicitation_telemetry_metadata(&enable_event),
+        None
+    );
+}
+
 #[test]
 fn guardian_elicitation_review_request_requires_opt_in() {
     let request = form_request(meta(json!({

codex-rs/core/src/session/tests.rs

@@ -328,13 +328,14 @@ async fn request_mcp_server_elicitation_auto_accepts_when_auto_deny_is_enabled()
         .await;
 
     assert_eq!(
-        response,
+        response.response,
         Some(ElicitationResponse {
             action: ElicitationAction::Accept,
             content: Some(json!({})),
             meta: None,
         })
     );
+    assert!(!response.sent);
     assert!(rx.try_recv().is_err());
 }