Mockserver MCP server

MockServer           

MockServer is an HTTP(S) mock server and proxy for testing. It does three things:

• Mock the APIs your application depends on, so you can develop and test against systems that are unavailable, incomplete, or hard to reproduce.
• Proxy real traffic to record, inspect, and modify requests and responses in flight — and pause them at interactive proxy breakpoints to step through, edit, or abort each exchange like a debugger for network traffic.
• Chaos engineering — make dependencies misbehave on demand, injecting latency, dropped connections, and errors to test how your application copes when the systems it relies on degrade or fail.

Speaks every protocol your stack uses. HTTP/1.1 & HTTPS, HTTP/2, gRPC & gRPC-Web, WebSockets and raw TCP are auto-detected from the first bytes of each connection, so one MockServer port handles them all with no per-protocol configuration. Beyond that core: HTTP/3 (QUIC — experimental, on its own UDP port), JSON-RPC for MCP/A2A mocking, AsyncAPI-driven message-broker testing against external Kafka and MQTT brokers, and mocked AI/LLM chat-completion APIs (OpenAI, Anthropic, Gemini, Bedrock, Azure OpenAI, Ollama).

Main Features

• Mock any API — HTTP/1.1, HTTPS, HTTP/2, HTTP/3, gRPC, gRPC-Web, JSON-RPC, WebSockets, raw TCP, and message brokers (Kafka, MQTT). Match requests on method, path, query, headers, cookies and body (JSON, XML, JSONPath, XPath, regex, OpenAPI) and return configured responses.
• Proxy & record — port forwarding, web (HTTP) proxy, HTTPS tunneling (CONNECT) and SOCKS, with full visibility of even TLS-encrypted traffic.
• Dynamic responses — response templating (Velocity, Mustache, JavaScript), class/closure callbacks and webhooks.
• OpenAPI — generate expectations directly from an OpenAPI/Swagger specification.
• Verification — assert which requests were received, in what order, and how many times.
• Chaos & resilience testing — inject latency, dropped/slow connections and failures to test how your system copes with a misbehaving dependency.
• LLM / AI mocking — mock chat-completion APIs for OpenAI, Anthropic, Gemini, Bedrock, Azure OpenAI and Ollama (including streaming), plus a built-in MCP server for AI coding assistants.
• Live dashboard — watch requests, expectations and logs in real time at /mockserver/dashboard.
• Clients & integrations — Java, JavaScript/Node, Python and Ruby clients, plus JUnit and Spring support.
• Run anywhere — Docker, Helm/Kubernetes, JAR or WAR, with optional clustered state for multi-instance deployments.

See the changelog for what has shipped in each version.

Getting started in 60 seconds

Run MockServer with Docker, then mock an endpoint and call it:

# 1. Start MockServer
docker run -d --rm -p 1080:1080 mockserver/mockserver

# 2. Mock an endpoint: GET /hello -> 200 "Hello World"

Shortened. The full README is on GitHub.