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MCPJam

MCPJam/inspector

Open-source testing and evaluation platform for MCP servers, for inspecting, chatting with, and debugging MCP servers, MCP apps, and ChatGPT apps.

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What is it?

MCPJam Inspector is a testing and evaluation platform for developers building MCP servers. It lets you run tools, resources, prompts, and elicitation flows by hand, and view full JSON-RPC logs and OAuth exchanges along the way. The Playground supports chatting with models against your server, including OpenAI Apps SDK and MCP app UIs, with a widget emulator for previewing layouts across desktop, tablet, and mobile sizes.

The project also covers evaluation and regression testing. You can define test cases with expected tool calls, run them across multiple LLMs, and track accuracy over time. A guided OAuth debugger checks conformance against several versions of the MCP authorization spec, including dynamic client registration and CIMD.

For automation, MCPJam ships a CLI and an SDK, and can run conformance, E2E, eval, and OAuth checks on each pull request in GitHub Actions or other CI systems. It is available as a hosted web app, a desktop app for Mac and Windows, or through npx and Docker.

Key features

  • 01Playground chat for testing tools against LLMs, with full traces of tool calls and JSON-RPC messages.
  • 02Widget emulator for OpenAI Apps SDK and MCP app UIs, with desktop, tablet, and mobile previews.
  • 03Guided OAuth debugger covering several MCP authorization spec versions, DCR, and CIMD.
  • 04Evals with expected tool calls and accuracy tracking across multiple LLMs.
  • 05CLI and SDK for probing servers and running checks from the terminal or your own tests.
  • 06CI/CD integration for running conformance, E2E, and eval checks on every PR.

Use cases

  • Debugging an MCP server's tools and prompts before connecting it to ChatGPT, Claude, or Cursor.
  • Checking an MCP server's OAuth setup step by step to locate authorization errors.
  • Running regression evals across several LLMs whenever tool definitions change.
  • Gating pull requests on MCP conformance tests in GitHub Actions.

Quick start

  1. 1

    Open the hosted app in your browser (no install needed)

  2. 2

    Or run MCPJam locally with Node.js 20+ via npx

    npx @mcpjam/inspector@latest

Things to know

  • The hosted web app supports only HTTPS server URLs, with no STDIO servers.
  • The terminal install requires Node.js 20 or newer.
  • The desktop app is available only for Mac and Windows.
  • The repository metadata shows no clear license (NOASSERTION), although the README states Apache 2.0.

Topics

#mcp#model-context-protocol#testing#evals#debugging#oauth#llm#cli#anthropic#chatgpt

FAQ

What is inspector?
Open-source testing and evaluation platform for MCP servers, for inspecting, chatting with, and debugging MCP servers, MCP apps, and ChatGPT apps. MCPJam Inspector is a testing and evaluation platform for developers building MCP servers. It lets you run tools, resources, prompts, and elicitation flows by hand, and view full JSON-RPC logs and OAuth exchanges along the way. The Playground supports chatting with models against your server, including OpenAI Apps SDK and MCP app UIs, with a widget emulator for previewing layouts across desktop, tablet, and mobile sizes.
Is inspector free to use? What license does it have?
inspector is open source under the Other license. Check the license terms before using it in commercial products.
Is inspector still maintained?
Actively maintained. The last commit to inspector was on Oct 22, 2026.
What can I use inspector for?
Debugging an MCP server's tools and prompts before connecting it to ChatGPT, Claude, or Cursor. Checking an MCP server's OAuth setup step by step to locate authorization errors. Running regression evals across several LLMs whenever tool definitions change. Gating pull requests on MCP conformance tests in GitHub Actions.
How do I install inspector?
Open the hosted app in your browser (no install needed) Or run MCPJam locally with Node.js 20+ via npx: npx @mcpjam/inspector@latest
Where can I get inspector?
The source code and installation instructions are on GitHub: https://github.com/MCPJam/inspector

Summary generated by AI from the project's README. GitHub stats refresh daily.

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