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MCP Inspector vs Postman in 2026: which one I actually use
The author encountered a common issue with MCP tool definitions where a typo in a field name between the schema and the handler caused an agent to ignore the tool. To address this, they tested three tools for validating MCP definitions: MCP Inspector, Postman, and a custom-built validator called MCP Tool Tester. MCP Inspector, the official debugger, requires a running server and identifies issues during runtime, which can be late. Postman also needs a running server and supports HTTP-based MCP, offering collaboration features but shallow validation. The author's MCP Tool Tester is a client-side validator that checks definitions instantly without a server, flagging issues like mismatched field names, long descriptions, and duplicate enum values. They use the validator for pre-deployment checks and Inspector for runtime testing. Postman is considered too heavy for quick definition checks but valuable for teams using HTTP servers. The validator excels at rapid, static definition validation, while Inspector is crucial for testing live tool behavior. Both the validator and Inspector serve distinct but complementary roles in the MCP development workflow.
