Joern MCP Server

Instructions

@param id: The unique identifier of the class (typeDecl), the id is a Long int string, like '111669149702L'
@return: The fully name of the class (e.g., com.android.nfc.NfcService$6)

Implementation Reference

• server_tools.py:57-65 (handler)

  The core handler function implementing the 'get_class_full_name_by_id' tool. It uses the joern_remote helper to query the Joern server and extract_value to parse the response.

  @joern_mcp.tool()
  def get_class_full_name_by_id(class_id:str) -> str:
      """Retrieves the fully name of a class by its ID
      
      @param id: The unique identifier of the class (typeDecl), the id is a Long int string, like '111669149702L'
      @return: The fully name of the class (e.g., com.android.nfc.NfcService$6)
      """
      response =  joern_remote(f'get_class_full_name_by_id("{class_id}")')
      return extract_value(response)

• server.py:94-106 (registration)

  Registers all tools from server_tools.py, including 'get_class_full_name_by_id', by dynamically executing the file containing the @joern_mcp.tool() decorators.

  SCRIPT_DIR = os.path.dirname(os.path.realpath(__file__))
  GENERATED_PY = os.path.join(SCRIPT_DIR, "server_tools.py")
  def generate():
      """Generate and execute additional server tools from server_tools.py file.
      
      This function reads the content of server_tools.py and executes it to add
      more functionality to the server.
      """
      with open(GENERATED_PY, "r") as f:
          code = f.read()
          exec(compile(code, GENERATED_PY, "exec"))
  
  generate()

• server.py:38-70 (helper)

  Key helper function used by the tool handler to send the actual query to the Joern server via HTTP.

  def joern_remote(query):
      """
      Execute remote query and return results
      
      Parameters:
      query -- The query string to execute
      
      Returns:
      Returns the server response stdout content on success
      Returns None on failure, error message will be output to stderr
      """
      data = {"query": query}
      headers = {'Content-Type': 'application/json'}
  
      try:
          response = requests.post(
              f'http://{server_endpoint}/query-sync',
              data=json.dumps(data),
              headers=headers,
              auth=basic_auth,
              timeout=timeout
          )
          response.raise_for_status()  
          
          result = response.json()
          return remove_ansi_escape_sequences(result.get('stdout', ''))
          
      except requests.exceptions.RequestException as e:
          sys.stderr.write(f"Request Error: {str(e)}\n")
      except json.JSONDecodeError:
          sys.stderr.write("Error: Invalid JSON response\n")
      
      return None