Local Inspector for MCP Apps & ChatGPT Apps SDK

Test and develop MCP apps (MCP-UI) and ChatGPT apps. Instantly view code changes locally, no more ngrok or ChatGPT subscription needed.

Start MCPJam in terminal:

npx@mcpjam/inspector@latest

Or download the desktop app

macOS Windows

Trusted by

Asana uses MCPJam to build ChatGPT and MCP apps

"MCPJam has helped save a ton of time for UI-related changes. We no longer have to do a two-minute deploy for every UI tweak."
Michael Chu, Engineering at Asana

Read the case study

ChatGPT Apps Builder

Like Chrome DevTools for ChatGPT Apps. Emulator that exposes all windows.openai API calls and JSON-RPC traffic, fully simulating ChatGPT's behavior.

OAuth debugger

Visualize and debug MCP authorization flows. Verify that your OAuth implementation conforms to the MCP spec at every step.

Read the guide

LLM playground

1:1 emulation with ChatGPT. Test your ChatGPT App against different models in the LLM playground. We provide frontier models such as GPT-5 for free. View in different display modes.