readme example throws error in Claude

[mmgreiner]

I ran the example in the readme.md weather_tool and Claude responded with the error:

[error] [weather_tool] [
  {
    "code": "invalid_union",
    "unionErrors": [
      {
        "issues": [
          {
            "code": "invalid_union",
            "unionErrors": [
              {
                "issues": [
                  {
                    "code": "invalid_type",
                    "expected": "string",
                    "received": "null",
                    "path": [
                      "id"
                    ],
                    "message": "Expected string, received null"
                  }
                ],
                "name": "ZodError"
              },
              {
                "issues": [
                  {
                    "code": "invalid_type",
                    "expected": "number",
                    "received": "null",
                    "path": [
                      "id"
                    ],
                    "message": "Expected number, received null"
                  }
                ],
                "name": "ZodError"
              }
            ],
            "path": [
              "id"
            ],
            "message": "Invalid input"
          },
          {
            "code": "invalid_type",
            "expected": "string",
            "received": "undefined",
            "path": [
              "method"
            ],
            "message": "Required"
          },
          {
            "code": "unrecognized_keys",
            "keys": [
              "error"
            ],
            "path": [],
            "message": "Unrecognized key(s) in object: 'error'"
          }
        ],
        "name": "ZodError"
      },
      {
        "issues": [
          {
            "code": "invalid_type",
            "expected": "string",
            "received": "undefined",
            "path": [
              "method"
            ],
            "message": "Required"
          },
          {
            "code": "unrecognized_keys",
            "keys": [
              "id",
              "error"
            ],
            "path": [],
            "message": "Unrecognized key(s) in object: 'id', 'error'"
          }
        ],
        "name": "ZodError"
      },
      {
        "issues": [
          {
            "code": "invalid_union",
            "unionErrors": [
              {
                "issues": [
                  {
                    "code": "invalid_type",
                    "expected": "string",
                    "received": "null",
                    "path": [
                      "id"
                    ],
                    "message": "Expected string, received null"
                  }
                ],
                "name": "ZodError"
              },
              {
                "issues": [
                  {
                    "code": "invalid_type",
                    "expected": "number",
                    "received": "null",
                    "path": [
                      "id"
                    ],
                    "message": "Expected number, received null"
                  }
                ],
                "name": "ZodError"
              }
            ],
            "path": [
              "id"
            ],
            "message": "Invalid input"
          },
          {
            "code": "invalid_type",
            "expected": "object",
            "received": "undefined",
            "path": [
              "result"
            ],
            "message": "Required"
          },
          {
            "code": "unrecognized_keys",
            "keys": [
              "error"
            ],
            "path": [],
            "message": "Unrecognized key(s) in object: 'error'"
          }
        ],
        "name": "ZodError"
      },
      {
        "issues": [
          {
            "code": "invalid_union",
            "unionErrors": [
              {
                "issues": [
                  {
                    "code": "invalid_type",
                    "expected": "string",
                    "received": "null",
                    "path": [
                      "id"
                    ],
                    "message": "Expected string, received null"
                  }
                ],
                "name": "ZodError"
              },
              {
                "issues": [
                  {
                    "code": "invalid_type",
                    "expected": "number",
                    "received": "null",
                    "path": [
                      "id"
                    ],
                    "message": "Expected number, received null"
                  }
                ],
                "name": "ZodError"
              }
            ],
            "path": [
              "id"
            ],
            "message": "Invalid input"
          }
        ],
        "name": "ZodError"
      }
    ],
    "path": [],
    "message": "Invalid input"
  }
]

I registered the tool in /Users/.../Library/Application Support/Claude/claude_desktop_config.json with:

"mcpServers": {
        "weather_tool": {
            "command": "/Users/mmgreiner/.local/share/mise/installs/ruby/3.4.5/bin/ruby",
            "args": [
                "/Users/mmgreiner/projects/Luzern-azure/LuzernConnect-KI/mcp/tiny_weather_server.rb"
            ]
        }
    }