"Understanding Sequential Thinking and Related Concepts" matching MCP connectors:

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

Free platform to test MCP clients without installing anything. Create mock tools with dynamic templates, configurable delays, conditions (if/then), and response sequences. Supports JSON-RPC 2.0 over Streamable HTTP. Built-in text_echo and json_echo tools. Rate-limited tiers: anonymous (5 calls/min, 1 mock tool), registered (10 calls/min, 4 mock tools), premium (60 calls/min, unlimited). Zero setup — no install, no registration required. More info: https://www.testmcp.dev

MCP tool observatory: do registry servers answer, and are their answers true? No key.

A webhook inbox for agents: one call returns a live URL. Mock, verify, inspect and replay.

Deterministic JSON checks with signed evidence and x402-paid execution

Deploy production REST APIs from JSON schemas in seconds. Manage projects, schemas, and deployments.

Discover, pay for, execute, and publish APIs through Apiosk.

Anonymous webhook capture, inspection, waiting, and response configuration for AI agents.

Instant no-signup webhook & HTTP-request inspector for testing webhooks and agent tool-callbacks.

Keyless webhook endpoints: capture, wait, replay, forward, and generate types from real traffic.

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

End-to-end API testing — generate and run tests from OpenAPI, curl, Postman, or real user traffic.

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

40+ developer tools from Context7, Code Runner, Python Execute, NPM Sentinel, PlantUML, and Microsoft Learn. Docs lookup, code execution, security scanning. Starts at $0.01/call. Get your API key at app.xpay.sh or xpay.tools

Public benchmark where agents submit Q&A answers and get scored on a leaderboard.

Conformance checker for MCP servers. Free, no key, verdicts recomputable and re-measured daily.

Manage your Nahook webhooks from your AI client — inspect deliveries, retry failures, and manage endpoints. Connects over OAuth, no API keys

MCP server and REST API for querying OpenAPI specs. Endpoint-level extraction, schema resolution, 100+ APIs indexed.

Search, document and execute authenticated API calls across 500+ apps via one MCP server

Public webhook inboxes for agents. Receive OAuth redirects, payment callbacks and CI notifications.