diff --git a/codex-rs/core/src/tools/spec.rs b/codex-rs/core/src/tools/spec.rs
index 5d681f64b..3a9c9eb58 100644
--- a/codex-rs/core/src/tools/spec.rs
+++ b/codex-rs/core/src/tools/spec.rs
@@ -1205,8 +1205,7 @@ fn create_close_agent_tool() -> ToolSpec {
 
     ToolSpec::Function(ResponsesApiTool {
         name: "close_agent".to_string(),
-        description: "Close an agent when it is no longer needed and return its last known status."
-            .to_string(),
+        description: "Close an agent when it is no longer needed and return its last known status. Don't keep agents open for too long if they are not needed anymore.".to_string(),
         strict: false,
         parameters: JsonSchema::Object {
             properties,