API Development MCP Servers for Codex CLI

What is known to be broken in an MCP server or API operation, with the check that found it.

Webhook, email, WebSocket and tunnel testing for AI agents: capture, wait, verify, replay.

Meaning of HTTP 410.

Meaning of HTTP 412.

Meaning of HTTP 418.

Meaning of HTTP 425.

Meaning of HTTP 502.

Meaning of HTTP 505.

HTTP reason-phrase catalog size

JSON Accept hint

JSON Schema keyword count, body discarded

Manage Nahook webhooks from your AI client: endpoints, deliveries, retries, environments.

Detect breaking changes, generate changelogs, diff, and validate OpenAPI specs.

Turn any task into the right API calls: discover, evaluate, and integrate public APIs.

Search otwarteAPI.pl: a catalog of public Polish & EU government/data APIs, for AI agents. Keyless.

Swagger Petstore API (v1.0.27) as MCP for testing and prototyping powered by the HAPI MCP server

Debug webhooks from your AI agent: inspect and replay captured webhooks on localhost.

HTTP status code reference MCP.

One MCP endpoint over 69 public PPN APIs: search_apis to discover, execute_api to call. Free tier.

protobuf3 message count, body discarded

Deterministic API regression checks for AI agents: snapshot a baseline, catch broken contracts.