diff --git a/codex-rs/core/src/tools/spec.rs b/codex-rs/core/src/tools/spec.rs
index 2cdd8ade23..f84fe38dc3 100644
--- a/codex-rs/core/src/tools/spec.rs
+++ b/codex-rs/core/src/tools/spec.rs
@@ -43,6 +43,8 @@ use codex_protocol::protocol::SubAgentSource;
 use codex_tools::CommandToolOptions;
 use codex_tools::FreeformTool;
 use codex_tools::FreeformToolFormat;
+use codex_tools::ResponsesApiNamespace;
+use codex_tools::ResponsesApiNamespaceTool;
 use codex_tools::ResponsesApiTool;
 use codex_tools::ShellToolOptions;
 use codex_tools::SpawnAgentToolOptions;
@@ -79,6 +81,7 @@ use serde::Serialize;
 use std::collections::BTreeMap;
 use std::collections::HashMap;
 use std::path::PathBuf;
+use std::sync::Arc;
 use std::sync::LazyLock;
 
 pub type JsonSchema = codex_tools::JsonSchema;
@@ -89,6 +92,8 @@ pub(crate) use codex_tools::mcp_call_tool_result_output_schema;
 const TOOL_SEARCH_DESCRIPTION_TEMPLATE_SOURCE: &str =
     include_str!("../../templates/search_tool/tool_description.md");
 const TOOL_SEARCH_DESCRIPTION_TEMPLATE_KEY: &str = "app_descriptions";
+const AGENT_TOOLS_NAMESPACE: &str = "agents";
+const AGENT_TOOLS_NAMESPACE_DESCRIPTION: &str = "Agent collaboration tools for spawning, messaging, waiting on, listing, and closing subagents.";
 static TOOL_SEARCH_DESCRIPTION_TEMPLATE: LazyLock<Template> = LazyLock::new(|| {
     Template::parse(TOOL_SEARCH_DESCRIPTION_TEMPLATE_SOURCE)
         .unwrap_or_else(|err| panic!("tool_search description template must parse: {err}"))
@@ -502,7 +507,10 @@ fn create_tool_search_tool(app_tools: &HashMap<String, ToolInfo>) -> ToolSpec {
             },
         ),
     ]);
-    let mut app_descriptions = BTreeMap::new();
+    let mut app_descriptions = BTreeMap::from([(
+        AGENT_TOOLS_NAMESPACE.to_string(),
+        Some(AGENT_TOOLS_NAMESPACE_DESCRIPTION.to_string()),
+    )]);
     for tool in app_tools.values() {
         if tool.server_name != CODEX_APPS_MCP_SERVER_NAME {
             continue;
@@ -958,6 +966,30 @@ fn push_tool_spec(
     }
 }
 
+fn create_agent_tools_namespace(tools: Vec<ToolSpec>) -> ToolSpec {
+    let tools = tools
+        .into_iter()
+        .filter_map(|tool| match tool {
+            ToolSpec::Function(tool) => Some(ResponsesApiNamespaceTool::Function(tool)),
+            _ => None,
+        })
+        .collect();
+
+    ToolSpec::Namespace(ResponsesApiNamespace {
+        name: AGENT_TOOLS_NAMESPACE.to_string(),
+        description: AGENT_TOOLS_NAMESPACE_DESCRIPTION.to_string(),
+        tools,
+    })
+}
+
+fn register_agent_tool_handler<H>(builder: &mut ToolRegistryBuilder, name: &str, handler: Arc<H>)
+where
+    H: crate::tools::registry::ToolHandler + 'static,
+{
+    builder.register_handler(name, handler.clone());
+    builder.register_handler(tool_handler_key(name, Some(AGENT_TOOLS_NAMESPACE)), handler);
+}
+
 /// Builds the tool registry builder while collecting tool specs for later serialization.
 #[cfg(test)]
 pub(crate) fn build_specs(
@@ -1012,8 +1044,6 @@ pub(crate) fn build_specs_with_discoverable_tools(
     use crate::tools::handlers::multi_agents_v2::SendMessageHandler as SendMessageHandlerV2;
     use crate::tools::handlers::multi_agents_v2::SpawnAgentHandler as SpawnAgentHandlerV2;
     use crate::tools::handlers::multi_agents_v2::WaitAgentHandler as WaitAgentHandlerV2;
-    use std::sync::Arc;
-
     let mut builder = ToolRegistryBuilder::new();
 
     let shell_handler = Arc::new(ShellHandler);
@@ -1202,9 +1232,8 @@ pub(crate) fn build_specs_with_discoverable_tools(
         builder.register_handler("request_permissions", request_permissions_handler);
     }
 
-    if config.search_tool
-        && let Some(app_tools) = app_tools
-    {
+    if config.search_tool && (app_tools.is_some() || config.collab_tools) {
+        let app_tools = app_tools.unwrap_or_default();
         let search_tool_handler = Arc::new(ToolSearchHandler::new(app_tools.clone()));
         push_tool_spec(
             &mut builder,
@@ -1348,102 +1377,67 @@ pub(crate) fn build_specs_with_discoverable_tools(
 
     if config.collab_tools {
         if config.multi_agent_v2 {
-            push_tool_spec(
-                &mut builder,
+            let agent_tools = vec![
                 create_spawn_agent_tool_v2(SpawnAgentToolOptions {
                     available_models: &config.available_models,
                     agent_type_description: crate::agent::role::spawn_tool_spec::build(
                         &config.agent_roles,
                     ),
                 }),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_send_message_tool(),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_assign_task_tool(),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_wait_agent_tool_v2(WaitAgentTimeoutOptions {
                     default_timeout_ms: DEFAULT_WAIT_TIMEOUT_MS,
                     min_timeout_ms: MIN_WAIT_TIMEOUT_MS,
                     max_timeout_ms: MAX_WAIT_TIMEOUT_MS,
                 }),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_close_agent_tool_v2(),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_list_agents_tool(),
+            ];
+            push_tool_spec(
+                &mut builder,
+                create_agent_tools_namespace(agent_tools),
                 /*supports_parallel_tool_calls*/ false,
                 config.code_mode_enabled,
             );
-            builder.register_handler("spawn_agent", Arc::new(SpawnAgentHandlerV2));
-            builder.register_handler("send_message", Arc::new(SendMessageHandlerV2));
-            builder.register_handler("assign_task", Arc::new(AssignTaskHandlerV2));
-            builder.register_handler("wait_agent", Arc::new(WaitAgentHandlerV2));
-            builder.register_handler("close_agent", Arc::new(CloseAgentHandlerV2));
-            builder.register_handler("list_agents", Arc::new(ListAgentsHandlerV2));
-        } else {
-            push_tool_spec(
+            register_agent_tool_handler(&mut builder, "spawn_agent", Arc::new(SpawnAgentHandlerV2));
+            register_agent_tool_handler(
                 &mut builder,
+                "send_message",
+                Arc::new(SendMessageHandlerV2),
+            );
+            register_agent_tool_handler(&mut builder, "assign_task", Arc::new(AssignTaskHandlerV2));
+            register_agent_tool_handler(&mut builder, "wait_agent", Arc::new(WaitAgentHandlerV2));
+            register_agent_tool_handler(&mut builder, "close_agent", Arc::new(CloseAgentHandlerV2));
+            register_agent_tool_handler(&mut builder, "list_agents", Arc::new(ListAgentsHandlerV2));
+        } else {
+            let agent_tools = vec![
                 create_spawn_agent_tool_v1(SpawnAgentToolOptions {
                     available_models: &config.available_models,
                     agent_type_description: crate::agent::role::spawn_tool_spec::build(
                         &config.agent_roles,
                     ),
                 }),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_send_input_tool_v1(),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            push_tool_spec(
-                &mut builder,
                 create_resume_agent_tool(),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
-            builder.register_handler("resume_agent", Arc::new(ResumeAgentHandler));
-            push_tool_spec(
-                &mut builder,
                 create_wait_agent_tool_v1(WaitAgentTimeoutOptions {
                     default_timeout_ms: DEFAULT_WAIT_TIMEOUT_MS,
                     min_timeout_ms: MIN_WAIT_TIMEOUT_MS,
                     max_timeout_ms: MAX_WAIT_TIMEOUT_MS,
                 }),
-                /*supports_parallel_tool_calls*/ false,
-                config.code_mode_enabled,
-            );
+                create_close_agent_tool_v1(),
+            ];
             push_tool_spec(
                 &mut builder,
-                create_close_agent_tool_v1(),
+                create_agent_tools_namespace(agent_tools),
                 /*supports_parallel_tool_calls*/ false,
                 config.code_mode_enabled,
             );
-            builder.register_handler("spawn_agent", Arc::new(SpawnAgentHandler));
-            builder.register_handler("send_input", Arc::new(SendInputHandler));
-            builder.register_handler("wait_agent", Arc::new(WaitAgentHandler));
-            builder.register_handler("close_agent", Arc::new(CloseAgentHandler));
+            register_agent_tool_handler(&mut builder, "spawn_agent", Arc::new(SpawnAgentHandler));
+            register_agent_tool_handler(&mut builder, "send_input", Arc::new(SendInputHandler));
+            register_agent_tool_handler(&mut builder, "resume_agent", Arc::new(ResumeAgentHandler));
+            register_agent_tool_handler(&mut builder, "wait_agent", Arc::new(WaitAgentHandler));
+            register_agent_tool_handler(&mut builder, "close_agent", Arc::new(CloseAgentHandler));
         }
     }
 
diff --git a/codex-rs/core/src/tools/spec_tests.rs b/codex-rs/core/src/tools/spec_tests.rs
index ffd3a03390..5405eaf65e 100644
--- a/codex-rs/core/src/tools/spec_tests.rs
+++ b/codex-rs/core/src/tools/spec_tests.rs
@@ -226,7 +226,8 @@ fn strip_descriptions_tool(spec: &mut ToolSpec) {
         ToolSpec::Function(ResponsesApiTool { parameters, .. }) => {
             strip_descriptions_schema(parameters);
         }
-        ToolSpec::Freeform(_)
+        ToolSpec::Namespace(_)
+        | ToolSpec::Freeform(_)
         | ToolSpec::LocalShell {}
         | ToolSpec::ImageGeneration { .. }
         | ToolSpec::WebSearch { .. } => {}
@@ -2220,7 +2221,8 @@ fn search_tool_description_handles_no_enabled_apps() {
         panic!("expected tool_search tool");
     };
 
-    assert!(description.contains("None currently enabled."));
+    assert!(description.contains("agents"));
+    assert!(description.contains("Agent collaboration tools for spawning, messaging, waiting on, listing, and closing subagents."));
     assert!(!description.contains("{{app_descriptions}}"));
 }
 
diff --git a/codex-rs/core/tests/suite/search_tool.rs b/codex-rs/core/tests/suite/search_tool.rs
index 423c57a8c6..984ef0cbf9 100644
--- a/codex-rs/core/tests/suite/search_tool.rs
+++ b/codex-rs/core/tests/suite/search_tool.rs
@@ -36,6 +36,7 @@ const SEARCH_TOOL_DESCRIPTION_SNIPPETS: [&str; 2] = [
     "- Calendar: Plan events and manage your calendar.",
 ];
 const TOOL_SEARCH_TOOL_NAME: &str = "tool_search";
+const AGENTS_NAMESPACE_TOOL_NAME: &str = "agents";
 const CALENDAR_CREATE_TOOL: &str = "mcp__codex_apps__calendar_create_event";
 const CALENDAR_LIST_TOOL: &str = "mcp__codex_apps__calendar_list_events";
 const SEARCH_CALENDAR_NAMESPACE: &str = "mcp__codex_apps__calendar";
@@ -217,7 +218,7 @@ async fn tool_search_disabled_by_default_exposes_apps_tools_directly() -> Result
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn search_tool_is_hidden_for_api_key_auth() -> Result<()> {
+async fn search_tool_keeps_agents_namespace_for_api_key_auth() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = start_mock_server().await;
@@ -247,8 +248,12 @@ async fn search_tool_is_hidden_for_api_key_auth() -> Result<()> {
     let body = mock.single_request().body_json();
     let tools = tool_names(&body);
     assert!(
-        !tools.iter().any(|name| name == TOOL_SEARCH_TOOL_NAME),
-        "tools list should not include {TOOL_SEARCH_TOOL_NAME} for API key auth: {tools:?}"
+        tools.iter().any(|name| name == TOOL_SEARCH_TOOL_NAME),
+        "tools list should include {TOOL_SEARCH_TOOL_NAME} for the always-present agents namespace: {tools:?}"
+    );
+    assert!(
+        tools.iter().any(|name| name == AGENTS_NAMESPACE_TOOL_NAME),
+        "tools list should include the {AGENTS_NAMESPACE_TOOL_NAME} namespace: {tools:?}"
     );
 
     Ok(())
diff --git a/codex-rs/tools/src/code_mode.rs b/codex-rs/tools/src/code_mode.rs
index ba6f68ae2d..45d3f014da 100644
--- a/codex-rs/tools/src/code_mode.rs
+++ b/codex-rs/tools/src/code_mode.rs
@@ -48,7 +48,8 @@ fn code_mode_tool_definition_for_spec(spec: &ToolSpec) -> Option<CodeModeToolDef
             input_schema: None,
             output_schema: None,
         }),
-        ToolSpec::LocalShell {}
+        ToolSpec::Namespace(_)
+        | ToolSpec::LocalShell {}
         | ToolSpec::ImageGeneration { .. }
         | ToolSpec::ToolSearch { .. }
         | ToolSpec::WebSearch { .. } => None,
diff --git a/codex-rs/tools/src/tool_spec.rs b/codex-rs/tools/src/tool_spec.rs
index f537388853..e9810d5157 100644
--- a/codex-rs/tools/src/tool_spec.rs
+++ b/codex-rs/tools/src/tool_spec.rs
@@ -1,5 +1,6 @@
 use crate::FreeformTool;
 use crate::JsonSchema;
+use crate::ResponsesApiNamespace;
 use crate::ResponsesApiTool;
 use codex_protocol::config_types::WebSearchContextSize;
 use codex_protocol::config_types::WebSearchFilters as ConfigWebSearchFilters;
@@ -15,6 +16,8 @@ use serde_json::Value;
 pub enum ToolSpec {
     #[serde(rename = "function")]
     Function(ResponsesApiTool),
+    #[serde(rename = "namespace")]
+    Namespace(ResponsesApiNamespace),
     #[serde(rename = "tool_search")]
     ToolSearch {
         execution: String,
@@ -52,6 +55,7 @@ impl ToolSpec {
     pub fn name(&self) -> &str {
         match self {
             ToolSpec::Function(tool) => tool.name.as_str(),
+            ToolSpec::Namespace(namespace) => namespace.name.as_str(),
             ToolSpec::ToolSearch { .. } => "tool_search",
             ToolSpec::LocalShell {} => "local_shell",
             ToolSpec::ImageGeneration { .. } => "image_generation",
diff --git a/codex-rs/tools/src/tool_spec_tests.rs b/codex-rs/tools/src/tool_spec_tests.rs
index c84ea94a36..5f76b29b45 100644
--- a/codex-rs/tools/src/tool_spec_tests.rs
+++ b/codex-rs/tools/src/tool_spec_tests.rs
@@ -6,6 +6,7 @@ use crate::AdditionalProperties;
 use crate::FreeformTool;
 use crate::FreeformToolFormat;
 use crate::JsonSchema;
+use crate::ResponsesApiNamespace;
 use crate::ResponsesApiTool;
 use crate::create_tools_json_for_responses_api;
 use codex_protocol::config_types::WebSearchContextSize;
@@ -47,6 +48,15 @@ fn tool_spec_name_covers_all_variants() {
         .name(),
         "tool_search"
     );
+    assert_eq!(
+        ToolSpec::Namespace(ResponsesApiNamespace {
+            name: "agents".to_string(),
+            description: "Agent tools".to_string(),
+            tools: Vec::new(),
+        })
+        .name(),
+        "agents"
+    );
     assert_eq!(ToolSpec::LocalShell {}.name(), "local_shell");
     assert_eq!(
         ToolSpec::ImageGeneration {
@@ -166,6 +176,24 @@ fn create_tools_json_for_responses_api_includes_top_level_name() {
     );
 }
 
+#[test]
+fn namespace_tool_spec_serializes_expected_wire_shape() {
+    assert_eq!(
+        serde_json::to_value(ToolSpec::Namespace(ResponsesApiNamespace {
+            name: "agents".to_string(),
+            description: "Agent collaboration tools.".to_string(),
+            tools: Vec::new(),
+        }))
+        .expect("serialize namespace"),
+        json!({
+            "type": "namespace",
+            "name": "agents",
+            "description": "Agent collaboration tools.",
+            "tools": []
+        })
+    );
+}
+
 #[test]
 fn web_search_tool_spec_serializes_expected_wire_shape() {
     assert_eq!(