"n8n - Workflow Automation Tool" matching MCP connectors:

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

AI-callable tools for API mocking, testing, monitoring, security, and automation.

Lints whether a paid API's 402 response speaks the x402 protocol correctly.

Free tools: x402 endpoint directory + probe, on-chain x402 demand signal, sudoku, API pricing.

{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"whoami","arguments":{}}} free no key

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

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

HttpStatus MCP Server — 24 AI-callable tools for API testing, mocking, monitoring, and security. Create and manage API mocks, run chaos engineering rules, validate OpenAPI specs, scan URLs for security issues, check SSL certificates, debug CORS, analyze redirect chains, decode JWTs, inspect HAR files, trace distributed requests, capture webhooks, build automation workflows (including Postman import), and set up uptime monitors — all from your AI assistant.

Search millions of x402 APIs for data, finance, validation, security, inventory, sync and automation

Check an MCP endpoint resolves: liveness, live tool list, schema drift. Free.

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

Check public MCP reachability, protocol handshake, auth and tool schemas before connecting.