MCP Inspector vs Postman in 2026: which one I actually use
I use two of the three: MCP Inspector for live calls, and a small client-side validator for checking definitions before I ever start a server. Postman's MCP support works, but it was too much setup for the quick checks I do most. Same broken tool, run through all three, below.
Full disclosure: the MCP Tool Tester I link to below is one I built. I'd tried four other validators and every one either needed a running server, an npm install, or an account before it'd tell me my inputSchema had a typo. Mine doesn't. It's free, runs entirely in your browser, no signup, nothing uploaded. Paste it in, get an answer. If you've got a better one, tell me.
The task: a broken currency tool
Three weeks ago I was wiring up an MCP server for a currency tool, and the agent kept refusing to call it. No error message. It just ignored the tool. After 47 minutes of squinting I found it: my handler read a field called from_currency, but the schema I advertised defined currency_from. The model saw a contract it couldn't satisfy and quietly walked away.
