Unable to Retrieve Tools on Cursor and Cline Using the Weather Example JAR

[jerryion]

After packaging the weather-stdio-server into a JAR, the ClientStdio in the test directory successfully retrieves the tools. However, when configuring MCP on Cursor and Cline as per the README, the connection is successful, but the available tools cannot be listed.

Environment: macOS 15.3.2, JDK 17

Cursor 0.47.8

Cline 3.8.0

[tomakehurst]

This looks like the same issue as #56

[devcrocod]

I checked the Cursor log:

2025-03-25 13:02:23.716 [info] ther: Handling CreateClient action
2025-03-25 13:02:23.716 [info] ther: getOrCreateClient for stdio server.  process.platform: darwin isElectron: true
2025-03-25 13:02:23.716 [info] ther: Starting new stdio process with command: java -jar /Users/pavel.gorgulov/Projects/main_project/mcp/kotlin-sdk/samples/weather-stdio-server/build/libs/weather-stdio-server-0.1.0-all.jar
2025-03-25 13:02:24.001 [info] ther: Successfully connected to stdio server
2025-03-25 13:02:24.001 [info] ther: Storing stdio client
2025-03-25 13:02:24.001 [info] ther: Handling ListOfferings action
2025-03-25 13:02:24.001 [info] ther: Listing offerings
2025-03-25 13:02:24.001 [info] ther: getOrCreateClient for stdio server.  process.platform: darwin isElectron: true
2025-03-25 13:02:24.001 [info] ther: Reusing existing stdio client
2025-03-25 13:02:24.001 [info] ther: Connected to stdio server, fetching offerings
2025-03-25 13:02:24.003 [error] ther: Error listing offerings: [
  {
    "code": "invalid_type",
    "expected": "array",
    "received": "undefined",
    "path": [
      "tools"
    ],
    "message": "Required"
  }
]

At the same time, the server responds correctly to the tools/list request:

{"jsonrpc": "2.0","id": 1,"method": "tools/list","params": {"cursor": "optional-cursor-value"}}
{"id":1,"jsonrpc":"2.0","result":{"tools":[{"name":"get_alerts","description":"Get weather alerts for a US state. Input is Two-letter US state code (e.g. CA, NY)","inputSchema":{"properties":{"state":{"type":"string","description":"Two-letter US state code (e.g. CA, NY)"}},"required":["state"],"type":"object"}},{"name":"get_forecast","description":"Get weather forecast for a specific latitude/longitude","inputSchema":{"properties":{"latitude":{"type":"number"},"longitude":{"type":"number"}},"required":["latitude","longitude"],"type":"object"}}],"_meta":{}}}

I verified this manually, both in the terminal and using the Inspector

[tomakehurst]

When I debugged this (with the latest versions of Cursor and the library), the server threw an exception at this line and didn't respond to Cursor:
https://github.com/modelcontextprotocol/kotlin-sdk/blob/main/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.util.kt#L141

The reason is that this server implementation expects the method attribute to be present in the params object in addition to its parent, whereas Cursor (and many other clients) only send it in the parent, with params empty.

[tomakehurst]

This fixes the issue (with Cursor at least), albeit in a bit of a hacky way:
https://github.com/modelcontextprotocol/kotlin-sdk/pull/58/files

[devcrocod]

@jerryion new version of kotlin-sdk 0.4.0, works great with Cursor in chat with agent mode.
Unfortunately, I can’t test it with Cline.

I’m closing this issue as resolved — if you encounter any problems with Cline, feel free to reopen the issue.

[tomakehurst]

Given that my PR isn't merged yet, how did this get fixed in the end?