feat: drop MCP managing tools if no MCP servers (#11900)

Drop MCP tools if no MCP servers to save context For this https://github.com/openai/codex/issues/11049
2026-04-24 14:45:27 +00:00 · 2026-02-16 18:40:45 +00:00
parent cef7fbc494
commit af434b4f71
5 changed files with 67 additions and 63 deletions
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -4997,14 +4997,13 @@ async fn built_tools(
    skills_outcome: Option<&SkillLoadOutcome>,
    cancellation_token: &CancellationToken,
 ) -> CodexResult<Arc<ToolRouter>> {
-    let mut mcp_tools = sess
-        .services
-        .mcp_connection_manager
-        .read()
-        .await
+    let mcp_connection_manager = sess.services.mcp_connection_manager.read().await;
+    let has_mcp_servers = mcp_connection_manager.has_servers();
+    let mut mcp_tools = mcp_connection_manager
        .list_all_tools()
        .or_cancel(cancellation_token)
        .await?;
+    drop(mcp_connection_manager);

    let mut effective_explicitly_enabled_connectors = explicitly_enabled_connectors.clone();
    effective_explicitly_enabled_connectors.extend(sess.get_connector_selection().await);
@@ -5050,12 +5049,12 @@ async fn built_tools(

    Ok(Arc::new(ToolRouter::from_config(
        &turn_context.tools_config,
-        Some(
+        has_mcp_servers.then(|| {
            mcp_tools
                .into_iter()
                .map(|(name, tool)| (name, tool.tool))
-                .collect(),
-        ),
+                .collect()
+        }),
        app_tools,
        turn_context.dynamic_tools.as_slice(),
    )))
--- a/codex-rs/core/src/mcp_connection_manager.rs
+++ b/codex-rs/core/src/mcp_connection_manager.rs
@@ -353,6 +353,10 @@ pub(crate) struct McpConnectionManager {
 }

 impl McpConnectionManager {
+    pub(crate) fn has_servers(&self) -> bool {
+        !self.clients.is_empty()
+    }
+
    pub async fn initialize(
        &mut self,
        mcp_servers: &HashMap<String, McpServerConfig>,
--- a/codex-rs/core/src/tools/spec.rs
+++ b/codex-rs/core/src/tools/spec.rs
@@ -1478,12 +1478,14 @@ pub(crate) fn build_specs(
        builder.register_handler("shell_command", shell_command_handler);
    }

-    builder.push_spec_with_parallel_support(create_list_mcp_resources_tool(), true);
-    builder.push_spec_with_parallel_support(create_list_mcp_resource_templates_tool(), true);
-    builder.push_spec_with_parallel_support(create_read_mcp_resource_tool(), true);
-    builder.register_handler("list_mcp_resources", mcp_resource_handler.clone());
-    builder.register_handler("list_mcp_resource_templates", mcp_resource_handler.clone());
-    builder.register_handler("read_mcp_resource", mcp_resource_handler);
+    if mcp_tools.is_some() {
+        builder.push_spec_with_parallel_support(create_list_mcp_resources_tool(), true);
+        builder.push_spec_with_parallel_support(create_list_mcp_resource_templates_tool(), true);
+        builder.push_spec_with_parallel_support(create_read_mcp_resource_tool(), true);
+        builder.register_handler("list_mcp_resources", mcp_resource_handler.clone());
+        builder.register_handler("list_mcp_resource_templates", mcp_resource_handler.clone());
+        builder.register_handler("read_mcp_resource", mcp_resource_handler);
+    }

    builder.push_spec(PLAN_TOOL.clone());
    builder.register_handler("update_plan", plan_handler);
@@ -1832,9 +1834,6 @@ mod tests {
        for spec in [
            create_exec_command_tool(true),
            create_write_stdin_tool(),
-            create_list_mcp_resources_tool(),
-            create_list_mcp_resource_templates_tool(),
-            create_read_mcp_resource_tool(),
            PLAN_TOOL.clone(),
            create_request_user_input_tool(),
            create_apply_patch_freeform_tool(),
@@ -2039,7 +2038,7 @@ mod tests {
            features,
            web_search_mode,
        });
-        let (tools, _) = build_specs(&tools_config, Some(HashMap::new()), None, &[]).build();
+        let (tools, _) = build_specs(&tools_config, None, None, &[]).build();
        let tool_names = tools.iter().map(|t| t.spec.name()).collect::<Vec<_>>();
        assert_eq!(&tool_names, &expected_tools,);
    }
@@ -2106,6 +2105,53 @@ mod tests {
        );
    }

+    #[test]
+    fn mcp_resource_tools_are_hidden_without_mcp_servers() {
+        let config = test_config();
+        let model_info =
+            ModelsManager::construct_model_info_offline_for_tests("gpt-5-codex", &config);
+        let mut features = Features::with_defaults();
+        features.enable(Feature::CollaborationModes);
+        let tools_config = ToolsConfig::new(&ToolsConfigParams {
+            model_info: &model_info,
+            features: &features,
+            web_search_mode: Some(WebSearchMode::Cached),
+        });
+        let (tools, _) = build_specs(&tools_config, None, None, &[]).build();
+
+        assert!(
+            !tools.iter().any(|tool| matches!(
+                tool.spec.name(),
+                "list_mcp_resources" | "list_mcp_resource_templates" | "read_mcp_resource"
+            )),
+            "MCP resource tools should be omitted when no MCP servers are configured"
+        );
+    }
+
+    #[test]
+    fn mcp_resource_tools_are_included_when_mcp_servers_are_present() {
+        let config = test_config();
+        let model_info =
+            ModelsManager::construct_model_info_offline_for_tests("gpt-5-codex", &config);
+        let mut features = Features::with_defaults();
+        features.enable(Feature::CollaborationModes);
+        let tools_config = ToolsConfig::new(&ToolsConfigParams {
+            model_info: &model_info,
+            features: &features,
+            web_search_mode: Some(WebSearchMode::Cached),
+        });
+        let (tools, _) = build_specs(&tools_config, Some(HashMap::new()), None, &[]).build();
+
+        assert_contains_tool_names(
+            &tools,
+            &[
+                "list_mcp_resources",
+                "list_mcp_resource_templates",
+                "read_mcp_resource",
+            ],
+        );
+    }
+
    #[test]
    fn test_build_specs_gpt5_codex_default() {
        let mut features = Features::with_defaults();
@@ -2116,9 +2162,6 @@ mod tests {
            Some(WebSearchMode::Cached),
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2138,9 +2181,6 @@ mod tests {
            Some(WebSearchMode::Cached),
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2162,9 +2202,6 @@ mod tests {
            &[
                "exec_command",
                "write_stdin",
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2186,9 +2223,6 @@ mod tests {
            &[
                "exec_command",
                "write_stdin",
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2208,9 +2242,6 @@ mod tests {
            Some(WebSearchMode::Cached),
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2230,9 +2261,6 @@ mod tests {
            Some(WebSearchMode::Cached),
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2252,9 +2280,6 @@ mod tests {
            Some(WebSearchMode::Cached),
            "shell",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "web_search",
@@ -2273,9 +2298,6 @@ mod tests {
            Some(WebSearchMode::Cached),
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -2297,9 +2319,6 @@ mod tests {
            &[
                "exec_command",
                "write_stdin",
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
--- a/codex-rs/core/tests/suite/model_tools.rs
+++ b/codex-rs/core/tests/suite/model_tools.rs
@@ -75,9 +75,6 @@ async fn model_selects_expected_tools() {
        expected_default_tools(
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -94,9 +91,6 @@ async fn model_selects_expected_tools() {
        expected_default_tools(
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -113,9 +107,6 @@ async fn model_selects_expected_tools() {
        expected_default_tools(
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
@@ -132,9 +123,6 @@ async fn model_selects_expected_tools() {
        expected_default_tools(
            "shell",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "web_search",
@@ -150,9 +138,6 @@ async fn model_selects_expected_tools() {
        expected_default_tools(
            "shell_command",
            &[
-                "list_mcp_resources",
-                "list_mcp_resource_templates",
-                "read_mcp_resource",
                "update_plan",
                "request_user_input",
                "apply_patch",
--- a/codex-rs/core/tests/suite/prompt_caching.rs
+++ b/codex-rs/core/tests/suite/prompt_caching.rs
@@ -144,9 +144,6 @@ async fn prompt_tools_are_consistent_across_requests() -> anyhow::Result<()> {
        vec!["exec_command", "write_stdin"]
    };
    expected_tools_names.extend([
-        "list_mcp_resources",
-        "list_mcp_resource_templates",
-        "read_mcp_resource",
        "update_plan",
        "request_user_input",
        "apply_patch",