Online Judge MCP Server

Instructions

Implementation Reference

• src/oj_mcp_server/server.py:30-41 (handler)

  The list_problems tool handler function that fetches problem list from the Online Judge. It accepts offset and limit parameters, uses get_authenticated_client() to ensure authentication, calls client.get_problems(), and returns the JSON result as a string.

  @mcp.tool()
  def list_problems(offset: int = 0, limit: int = 50) -> str:
      """
      Fetch the list of problems from the Online Judge.
      Returns a JSON string containing total count and results.
      """
      c = get_authenticated_client()
      try:
          data = c.get_problems(offset=offset, limit=limit)
          return str(data)
      except Exception as e:
          return f"Error: {e}"

• src/oj_mcp_server/server.py:21-28 (helper)

  Helper function get_authenticated_client() used by list_problems to ensure the user is logged in before making API calls. Handles lazy initialization of authentication using environment variables.

  def get_authenticated_client():
      global is_logged_in
      if not is_logged_in:
          if not OJ_USERNAME or not OJ_PASSWORD:
              raise ValueError("OJ_USERNAME and OJ_PASSWORD environment variables are required.")
          client.login(OJ_USERNAME, OJ_PASSWORD)
          is_logged_in = True
      return client

• src/oj_mcp_server/oj_client.py:42-46 (helper)

  The get_problems() method in OJClient that makes the actual HTTP GET request to /api/problem endpoint with pagination parameters (offset, limit) and returns the JSON response.

  def get_problems(self, offset=0, limit=50):
      params = {'paging': 'true', 'offset': offset, 'limit': limit}
      resp = self.session.get(self._get_url("/api/problem"), params=params, timeout=20)
      resp.raise_for_status()
      return resp.json()