[vishalhabib99]

Problem

In supporting-blog-content/elasticsearch-typescript-claude-mcp/index.ts, the semantic_search error path calls console.log("Error during search:", error). The server runs over StdioServerTransport, where stdout is the JSON-RPC stream, and the MCP docs say a stdio server must never write anything else there. Node prints the error object with its stack, so one failed search (a missing index, a bad API key) puts several non-JSON lines on the stream, and the client logs parse errors for each.

Change

console.log -> console.error on that line, so the message goes to stderr. The tool still returns the same isError: true result.

Checked

Standalone stdio server with the same tool shape on @modelcontextprotocol/sdk 1.32.2 (within ^1.20.0), throwing from the search and calling tools/call once:

	stdout lines	not JSON
console.log (main)	8	6
console.error (this branch)	2	0

[gitnotebooks]

Review these changes at https://app.gitnotebooks.com/elastic/elastic-labs/pull/608