The LangWatch MCP Server is a tool designed to aid finding, searching, and looking up LLM traces from the LangWatch platform via the Model Context Protocol. This server facilitates LLM development by allowing the agent to search for traces, understand all the steps in between a problematic output and try to fix the issue.

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Setup in your Codebase

Check out the integration guides to start tracking your agents so both you and Cursor/Windsurf/Claude Code or your favorite coding assistant can debug it.

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Setup in Cursor 👩‍💻

  1. Navigate to the Cursor Settings
  2. Navigate to the MCP item in the sidebar
  3. Set the “name” as “LangWatch”
  4. Set the “type” to command
  5. Set the “command” to npx -y @langwatch/mcp-server --apiKey=sk-lw-...
  • --apiKey: Your LangWatch API key. This is mandatory and must be provided.
  • --endpoint: Optional The endpoint for the LangWatch API. Defaults to https://app.langwatch.ai if not specified.
To aid in securing your keys, the MCP will first look at the global system environment variables LANGWATCH_API_KEY and LANGWATCH_ENDPOINT to check if they have values as well as looking at arguments passed into the server on start.
LangWatch MCP Setup

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Tools

The MCP Server provides the following tools:

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get_latest_traces

  • Description: Retrieves the latest LLM traces.
  • Parameters:
    • pageOffset (optional): The page offset for pagination.
    • daysBackToSearch (optional): The number of days back to search for traces. Defaults to 1.

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get_trace_by_id

  • Description: Retrieves a specific LLM trace by its ID.
  • Parameters:
    • id: The ID of the trace to retrieve.

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Usage in Cursor

To use these tools within Cursor, follow these steps:
  1. Open the Cursor Chat view:
    • Cmd + I
  2. Ensure the MCP server is running:
  3. Interact with your Agent:
    • Ask a question like the following to test the tools are accessible: *Note: When the tool is detected, you’ll need to run Run tool in the chat view for it to be called.
“I just ran into an issue while debugging, can you check the latest traces and fix it?”
LangWatch MCP Example

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🛟 Support

If you have questions or need help, join our community: