An MCP server validates JSON, OpenAPI and SQL before agents execute actions
Desperate-Guide-5073 · reddit · 2026-07-23
The author built an MCP server for deterministic output validation that checks JSON Schema, OpenAPI responses, and SQL syntax before an agent acts on generated output.
Why it exists
The main failure mode was downstream: a model emits something almost valid, the pipeline breaks later, and the author ends up paying for retries or debugging. The service treats invalid output as a normal result, not an HTTP error.
What it returns
- A typed verdict: valid or invalid
- Errors with paths and fix hints
- latencyms
How to use it
- Remote streamable HTTP endpoint: no install required
- stdio adapter via npm: @/machinegrade/validate
- Listed in the official MCP registry and on Smithery
- Free tier: 500 calls/month
The project is MIT licensed and self-hostable, but the author says this is also a demand test for whether a hosted validator is worth paying for.
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