list_modal_volumes

Instructions

List all Modal volumes using the Modal CLI with JSON output.

Returns:
    A dictionary containing the parsed JSON output of the Modal volumes list.

Implementation Reference

• src/modal_mcp/server.py:95-111 (handler)

  The main handler function for the 'list_modal_volumes' tool. It executes the Modal CLI command 'modal volume list --json', processes the JSON output using helper functions, and returns a standardized dictionary with volumes list or error details.

  @mcp.tool()
  async def list_modal_volumes() -> dict[str, Any]:
      """
      List all Modal volumes using the Modal CLI with JSON output.
  
      Returns:
          A dictionary containing the parsed JSON output of the Modal volumes list.
      """
      try:
          result = run_modal_command(["modal", "volume", "list", "--json"])
          response = handle_json_response(result, "Failed to list volumes")
          if response["success"]:
              return {"success": True, "volumes": response["data"]}
          return response
      except Exception as e:
          logger.error(f"Failed to list Modal volumes: {e}")
          raise

• src/modal_mcp/server.py:15-40 (helper)

  Core helper function used by list_modal_volumes to execute shell commands via subprocess, capturing stdout/stderr and handling errors.

  def run_modal_command(command: list[str], uv_directory: str = None) -> dict[str, Any]:
      """Run a Modal CLI command and return the result"""
      try:
          # uv_directory is necessary for modal deploy, since deploying the app requires the app to use the uv venv
          command = (["uv", "run", f"--directory={uv_directory}"] if uv_directory else []) + command
          logger.info(f"Running command: {' '.join(command)}")
          result = subprocess.run(
              command,
              capture_output=True,
              text=True,
              check=True
          )
          return {
              "success": True,
              "stdout": result.stdout,
              "stderr": result.stderr,
              "command": ' '.join(command)
          }
      except subprocess.CalledProcessError as e:
          return {
              "success": False,
              "error": str(e),
              "stdout": e.stdout,
              "stderr": e.stderr,
              "command": ' '.join(command)
          }

• src/modal_mcp/server.py:42-70 (helper)

  Helper function called by list_modal_volumes to parse JSON from command stdout and standardize the response format with success/error handling.

  def handle_json_response(result: Dict[str, Any], error_prefix: str) -> Dict[str, Any]:
      """
      Handle JSON parsing of command output and return a standardized response.
      
      Args:
          result: The result from run_modal_command
          error_prefix: Prefix to use in error messages
          
      Returns:
          A dictionary with standardized success/error format
      """
      if not result["success"]:
          response = {"success": False, "error": f"{error_prefix}: {result.get('error', 'Unknown error')}"}
          if result.get("stdout"):
              response["stdout"] = result["stdout"]
          if result.get("stderr"):
              response["stderr"] = result["stderr"]
          return response
      
      try:
          data = json.loads(result["stdout"])
          return {"success": True, "data": data}
      except json.JSONDecodeError as e:
          response = {"success": False, "error": f"Failed to parse JSON output: {str(e)}"}
          if result.get("stdout"):
              response["stdout"] = result["stdout"]
          if result.get("stderr"):
              response["stderr"] = result["stderr"]
          return response

• src/modal_mcp/server.py:95-95 (registration)

  The @mcp.tool() decorator registers the list_modal_volumes function as an MCP tool.

  @mcp.tool()