shell tool: move shell usage instructions from prompt to tool description (#6473)

codex-rs/core/gpt_5_codex_prompt.md

@@ -2,8 +2,6 @@ You are Codex, based on GPT-5. You are running as a coding agent in the Codex CL
 
 ## General
 
-- The arguments to `shell` will be passed to execvp(). Most terminal commands should be prefixed with ["bash", "-lc"].
-- Always set the `workdir` param when using the shell function. Do not use `cd` unless absolutely necessary.
 - When searching for text or files, prefer using `rg` or `rg --files` respectively because `rg` is much faster than alternatives like `grep`. (If the `rg` command is not found, then use alternatives.)
 
 ## Editing constraints

codex-rs/core/src/tools/spec.rs

@@ -181,8 +181,11 @@ fn create_exec_command_tool() -> ToolSpec {
     ToolSpec::Function(ResponsesApiTool {
         name: "exec_command".to_string(),
         description:
-            "Runs a command in a PTY, returning output or a session ID for ongoing interaction."
-                .to_string(),
+            concat!(
+              "Runs a command in a PTY, returning output or a session ID for ongoing interaction.\n",
+              "- Always set the `workdir` param when using the shell function. Do not use `cd` unless absolutely necessary."
+            )
+            .to_string(),
         strict: false,
         parameters: JsonSchema::Object {
             properties,
@@ -274,7 +277,12 @@ fn create_shell_tool() -> ToolSpec {
 
     ToolSpec::Function(ResponsesApiTool {
         name: "shell".to_string(),
-        description: "Runs a shell command and returns its output.".to_string(),
+        description: concat!(
+            "Runs a shell command and returns its output.\n",
+            "- The value of `command` will be passed to execvp(). Most terminal commands should be prefixed with [`bash`, `-lc`].\n",
+            "- Always set the `workdir` param when using the shell function. Do not use `cd` unless absolutely necessary.",
+        )
+        .to_string(),
         strict: false,
         parameters: JsonSchema::Object {
             properties,
@@ -1726,7 +1734,7 @@ mod tests {
         };
         assert_eq!(name, "shell");
 
-        let expected = "Runs a shell command and returns its output.";
+        let expected = "Runs a shell command and returns its output.\n- The value of `command` will be passed to execvp(). Most terminal commands should be prefixed with [`bash`, `-lc`].\n- Always set the `workdir` param when using the shell function. Do not use `cd` unless absolutely necessary.";
         assert_eq!(description, expected);
     }