koala73/worldmonitor · error

tools/list error: ${listData.error.message}

Error message

tools/list error: ${listData.error.message}

What it means

Thrown by mcpListTools when the tools/list JSON-RPC call returned HTTP 2xx but the response payload contained a JSON-RPC error object. The MCP server explicitly reported a protocol-level error while enumerating tools (e.g. unknown method, internal server error in the handler).

Source

Thrown at api/mcp-proxy.ts:324

    if (error instanceof McpProxySsrfError) throw error;
    /* non-fatal */
  }
}

async function mcpListTools(serverUrl, customHeaders) {
  const headers = buildHeaders(customHeaders);
  const initResp = await postJson(serverUrl, buildInitPayload(), headers, null);
  if (!initResp.ok) throw new Error(`Initialize failed: HTTP ${initResp.status}`);
  const sessionId = initResp.headers.get('Mcp-Session-Id') || initResp.headers.get('mcp-session-id');
  const initData = await parseJsonRpcResponse(initResp);
  if (initData.error) throw new Error(`Initialize error: ${initData.error.message}`);
  await sendInitialized(serverUrl, headers, sessionId);
  const listResp = await postJson(serverUrl, {
    jsonrpc: '2.0', id: 2, method: 'tools/list', params: {},
  }, headers, sessionId);
  if (!listResp.ok) throw new Error(`tools/list failed: HTTP ${listResp.status}`);
  const listData = await parseJsonRpcResponse(listResp);
  if (listData.error) throw new Error(`tools/list error: ${listData.error.message}`);
  return listData.result?.tools || [];
}

async function mcpCallTool(serverUrl, toolName, toolArgs, customHeaders) {
  const headers = buildHeaders(customHeaders);
  const initResp = await postJson(serverUrl, buildInitPayload(), headers, null);
  if (!initResp.ok) throw new Error(`Initialize failed: HTTP ${initResp.status}`);
  const sessionId = initResp.headers.get('Mcp-Session-Id') || initResp.headers.get('mcp-session-id');
  const initData = await parseJsonRpcResponse(initResp);
  if (initData.error) throw new Error(`Initialize error: ${initData.error.message}`);
  await sendInitialized(serverUrl, headers, sessionId);
  const callResp = await postJson(serverUrl, {
    jsonrpc: '2.0', id: 3, method: 'tools/call',
    params: { name: toolName, arguments: toolArgs || {} },
  }, headers, sessionId);
  if (!callResp.ok) throw new Error(`tools/call failed: HTTP ${callResp.status}`);
  const callData = await parseJsonRpcResponse(callResp);
  if (callData.error) throw new Error(`tools/call error: ${callData.error.message}`);

View on GitHub (pinned to 9361220cc0)

Solutions

1. Read the embedded error.message — it is the upstream server's JSON-RPC error text
2. Verify the server supports the tools/list method in its advertised capabilities
3. Restart or reconfigure the MCP server if it reports an internal tool listing failure

When it happens

Trigger: Thrown at api/mcp-proxy.ts:322 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of koala73/worldmonitor@9361220cc0 (2026-08-21). Data as JSON: /api/errors/6ff4cdd5d688713b. Report an issue: GitHub.