MCPJam is the development platform for MCP servers, MCP apps, and ChatGPT apps.
- Debug: Inspect every JSON-RPC message and OAuth exchange across host configurations with full traces.
- Chat: Talk to any LLM against your server with full trace visibility into tool calls and context across agent, host app, your server.
- Inspect: Explore your serverβs tools, resources, and prompts in one place.
- Evaluate: Run evals across multiple LLMs and track accuracy over time so you catch regressions early.
- CLI: Probe servers, run doctor checks, exercise OAuth flows, and list tools/resources/prompts straight from your terminal.
- SDK: Programmatically drive inspections, snapshot server capabilities, and assert on tool/resource shapes from your own tests.
- CI/CD: Wire the CLI and SDK into GitHub Actions (or any pipeline) to run e2e tests, evals, OAuth checks, and spec conformance on every PR.
No more ngrok or ChatGPT/Claude subscription needed. MCPJam is the fastest way to iterate on any MCP project.
Open the hosted web app. No install needed.
π app.mcpjam.com
Or run MCPJam locally for HTTP/S and local STDIO servers:
npx @mcpjam/inspector@latest
MCPJam Inspector runs three ways: a hosted web app, a desktop app for Mac and Windows, or via your terminal. The web app is HTTPS-only and has no install. Terminal and Desktop support HTTP/S and local STDIO servers.
Node.js 20+ is only required for the terminal install (npx). The hosted web app and desktop apps have no local runtime requirements.
Open app.mcpjam.com in your browser. No install required. Always on the latest version, and you can share MCP server links with teammates the same way you'd share a Google Doc.
- HTTPS MCP server URLs only (for HTTP or local STDIO servers, use Desktop or Terminal).
- No STDIO, tunneling, skills, or tasks. Those require the local inspector.
See Hosted App docs for details.
Download the installer for your OS. Supports HTTP/S and local STDIO servers. No Node.js required.
Run the inspector via npx (supports HTTP/S and local STDIO):
npx @mcpjam/inspector@latestAfter it starts, open the printed localhost URL in your browser.
Run MCPJam Inspector using Docker, bound to localhost for security:
docker run -p 127.0.0.1:6274:6274 mcpjam/mcp-inspectorThe app is available at http://127.0.0.1:6274. Always use -p 127.0.0.1:6274:6274 (not -p 6274:6274) to keep the inspector local-only. On macOS/Windows, connect to host MCP servers via http://host.docker.internal:PORT instead of 127.0.0.1.
| Capability | Description |
|---|---|
| App Builder | Debug your server against a model: tool calls or in-panel chat, with Chat, Trace, and Raw. OpenAI Apps SDK and MCP app UIs, text tools, Chrome DevTools-style widget emulator. Read more |
| Chat | Multi-server chat on frontier models (free). Chat, Trace, Raw; compare up to 3 models. Read more |
| OAuth Debugger | Guided MCP OAuth conformance checks: protocol versions 03-26, 06-18, 11-25; DCR, client pre-registration, CIMD. Read more |
| MCP Server Debugging | Manually run tools, resources, templates, and elicitation; full JSON-RPC logs. |
| Skills | Skills in Chat and App Builder; local filesystem only. Read more |
| Workspaces | Shared server groups with real-time team sync. Read more |
| Evals | Test cases with expected tool calls, run across LLMs, metrics. Read more |
| CLI | Run MCPJam checks, probes, and evals from the terminal. Perfect for local dev loops and CI. Read more |
| SDK | Programmatic access to MCPJam for custom tooling, scripting, and integrations. Read more |
| CI/CD | Run MCPJam checks and evals in GitHub Actions and other CI systems to gate PRs on regressions. Read more |
Debug your server against a model using tool calls or in-panel chat, with Chat, Trace, and Raw views. Supports OpenAI Apps SDK and MCP app UIs, text tools, and a Chrome DevTools-style widget emulator to iterate on widgets locally.
- Manually invoke a tool to instantly view the widget, or chat with your server using an LLM.
- View all JSON-RPC messages and
window.openaimessages in the logs. - Change emulator device to Desktop, Tablet, or Mobile views.
- Test your app's locale change, CSP permissions, light / dark mode, hover & touch, and safe area insets.
Trace view: every tool call, agent step, and JSON-RPC message.
Multi-server chat on frontier models for free, or bring your own API key. Chat, Trace, and Raw views; compare up to 3 models side-by-side. View your server's token usage.
Guided MCP OAuth conformance checks with step-by-step explanations. Test against every version of the OAuth spec (03-26, 06-18, and 11-25). Support for client pre-registration, Dynamic Client Registration (DCR), and Client ID Metadata Documents (CIMD).
MCPJam contains all of the tooling to test your MCP server. Manually run tools, resources, resource templates, prompts, and elicitation flows, with full JSON-RPC observability. MCPJam has all features from the original inspector and more.
Use Skills in Chat and App Builder to extend models with local, reusable behaviors. Local filesystem only. Your data never leaves your machine. Read more
Group your servers into shared workspaces with real-time team sync, so everyone on your team is testing against the same configuration. Read more
Define test cases with expected tool calls and run them across multiple LLMs. Track accuracy metrics over time to catch regressions early and improve your server with every iteration. Read more
Run MCPJam from the terminal for fast local dev loops and CI integration. Probe servers, run OAuth checks, inspect tools and resources, and execute evals without leaving your shell. Read more
Programmatic access to MCPJam for custom tooling, scripting, and integrations. Build your own workflows on top of MCPJam's inspection and evaluation primitives. Read more
Wire MCPJam into GitHub Actions, GitLab CI, or your CI system of choice to run conformance, E2E tests, and evals on every PR. Catch MCP server regressions before they ship. Read more
We're grateful for you considering contributing to MCPJam. Please read our contributing guide.
Join our Discord community where the contributors hang out at.
Some of our partners and favorite frameworks:
- Stytch. Our favorite MCP OAuth provider.
- xMCP. The Typescript MCP framework. Ship on Vercel instantly.
- Alpic. Host MCP servers. Try their new Skybridge framework for ChatGPT apps!
This project is licensed under the Apache License 2.0. See the LICENSE.