@mockzilla/mcp

MCP server for Mockzilla - an open-source API mock server for OpenAPI specifications. Let Claude Code, Claude Desktop, Cursor, or Gemini CLI install Mockzilla, inspect OpenAPI specs, and spin up realistic local mock APIs in seconds. No account required for local use.

Source: github.com/mockzilla/mockzilla-mcp

Use cases

• Local API development - mock any OpenAPI spec without a real backend or sandbox account
• CI/CD integration testing - zero external dependencies in your pipeline
• PSP and payment API mocking - Stripe, PayPal, Adyen from your editor without test accounts
• Crypto exchange API mocking - Binance, Bybit without registered accounts
• Rate limit protection - develop against OpenAI, Twilio without burning quota
• Agentic workflows - let Claude or Cursor spin up and manage mock servers automatically

Two planes

@mockzilla/mcp exposes two planes of tools to your MCP client.

Local plane (no account required)

Works entirely on your machine. Nothing leaves the user's box.

From an agent you can:

• Check whether the Mockzilla CLI is installed.
• Install Mockzilla into a managed cache (no changes to system PATH).
• Inspect an OpenAPI spec (title, version, endpoint count, paths).
• Serve any OpenAPI spec locally as a portable mock server.
• Mock a single HTTP endpoint without a spec.
• List, stop, and clear locally managed mocks.

Hosted plane (requires MOCKZILLA_TOKEN)

When MOCKZILLA_TOKEN is set, the bridge forwards extra tools to mockzilla.org's MCP endpoint.

Agents can then:

• List deployed sims.
• Browse catalog products.
• Deploy hosted mocks from a spec, URL, or catalog bundle.
• Wait for a deploy and return the live URL.

Without a token, only the local plane is exposed. Agents can still help users explore Mockzilla and run local mocks before they sign up.

Example prompts

You can use these directly from Claude Code, Claude Desktop, Cursor, or Gemini CLI once mockzilla is configured as an MCP server.

Local plane (no token)

• "Is the mockzilla CLI installed on this machine?"
• "Install Mockzilla for me."
• "Spin up the Petstore OpenAPI spec locally so I can curl it."
• "What endpoints does https://example.com/openapi.yaml expose?"
• "Mock POST /checkout to return a 402 response."
• "List the mock endpoints you're managing."
• "Stop the mock server you started."

Hosted plane (with MOCKZILLA_TOKEN)

• "List the sims I have deployed."
• "Show me the catalog products."
• "Deploy a Stripe sandbox named stripe-test and give me the live URL."
• "Create a hosted mock from this OpenAPI URL on mockzilla.org."

Install

Claude Code

One-liner, no config file editing:

claude mcp add -s user mockzilla -- npx -y @mockzilla/mcp@latest

• -s user installs for your user account (available in every project).
• Drop -s user to scope to the current project only.

Claude Desktop

Edit ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "mockzilla": {
      "command": "npx",
      "args": ["-y", "@mockzilla/mcp@latest"]
    }
  }
}

Restart Claude Desktop after editing.

Cursor

Easiest: Settings -> MCP Servers -> Add new MCP server and fill in:

• Name: mockzilla
• Command: npx
• Args: -y @mockzilla/mcp@latest

Or edit ~/.cursor/mcp.json directly:

{
  "mcpServers": {
    "mockzilla": {
      "command": "npx",
      "args": ["-y", "@mockzilla/mcp@latest"]
    }
  }
}

Restart Cursor after editing.

Gemini CLI

One-liner, no manual JSON editing:

gemini mcp add -s user mockzilla npx -y @mockzilla/mcp@latest

• -s user writes to ~/.gemini/settings.json (available in every project).
• Drop -s user (or use -s project) to scope to the current directory's .gemini/settings.json.

Or edit the settings file directly:

{
  "mcpServers": {
    "mockzilla": {
      "command": "npx",
      "args": ["-y", "@mockzilla/mcp@latest"]
    }
  }
}

Restart the Gemini CLI after editing.

Why @latest?

Without @latest, npx caches the first resolved version and won't pick up new publishes. Pinning to @latest makes npx re-check the registry on every spawn, so a Claude / Cursor / Gemini restart is enough to upgrade. Trade-off: ~200 ms extra startup time.

Local tools

These tools are always available and never leave the user's machine.

Setup and status

• check_cli Resolve Mockzilla on this machine: system PATH -> bridge cache -> go run invocation. Returns install options if nothing matches.

• install_cli Install Mockzilla into ~/.cache/mockzilla-mcp/. Methods: download (prebuilt from GitHub releases, default), go-install, go-run. Never touches system PATH.

• bridge_status Report the bridge's version, check npm for newer publishes, and surface upgrade steps.

OpenAPI exploration and docs

• peek_openapi Summarise an OpenAPI spec without serving it: {title, version, openapi_version, endpoint_count, paths}.

• mockzilla_docs_topics List available Mockzilla doc topics.

• mockzilla_docs_read Return the full markdown for one topic.

• mockzilla_docs_search Keyword search across all docs; returns top sections with snippets.

Local mocking

• serve_locally Start a portable mock server on a free port. Accepts a spec file, directory, or public https URL. Returns {url, port, pid, services}.

• stop_locally Stop a server started by serve_locally.

• mock_endpoint Quickly mock a single HTTP endpoint without an OpenAPI spec. Writes a static response into the managed mocks dir and (re)starts the shared server.

• list_mock_endpoints List all endpoints currently mocked, plus the running server's URL and the Mockzilla UI URL.

• clear_mock_endpoints Wipe all mocks and stop the managed server.

Hosted tools

When MOCKZILLA_TOKEN is set, @mockzilla/mcp forwards hosted tools to mockzilla.org's MCP endpoint.

At the time of writing, the hosted surface includes:

• get_context
• list_sims
• list_catalog_products
• deploy_mock_from_catalog
• deploy_mock_from_spec
• deploy_mock_from_url
• wait_for_deploy

Refer to the hosted server's docs or the MCP registry entry for the live tool list.

Configuration

Cache layout

The bridge keeps everything under ~/.cache/mockzilla-mcp/:

~/.cache/mockzilla-mcp/
├── bin/mockzilla        # downloaded or go-installed binary
├── config.json          # { method, version, invocation? }
└── mocks/               # mock_endpoint persists static endpoints here
    └── static/
        └── <service>/<path>/<method>/index.<ext>

• rm -rf ~/.cache/mockzilla-mcp fully resets the bridge (binary + all mocked endpoints).
• To wipe just the mocks: rm -rf ~/.cache/mockzilla-mcp/mocks.
• The system PATH is never touched, so reset doesn't affect a separate brew install of Mockzilla.

Updates

Recommended way to stay current:

1. Pin @mockzilla/mcp@latest in your MCP client config so npx re-checks the registry on every spawn.
2. Restart Claude Desktop / Cursor / Gemini periodically. That's when the new tarball is fetched.
3. If something seems off, ask the agent: "Run bridge_status and tell me if @mockzilla/mcp is up to date."

If it's stale, run:

npx clear-npx-cache @mockzilla/mcp

and restart your MCP client.

The Mockzilla CLI version is pinned by the bridge (via MOCKZILLA_VERSION in lib/install.js). Updating the bridge updates the pin; the next install_cli call brings the CLI itself up to date.

Development

See CLAUDE.md for project conventions and a walkthrough of adding a new tool.

Releasing

The bridge has two registries to keep in sync: npm (@mockzilla/mcp) and the MCP registry (server.json). Skipping the second one leaves discovery clients pinned to the previous tarball.

1. Bump version in package.json.

2. Run:

   bash

   Copy

   make publish-all
   

   This will:

   • Run the smoke test.
   • npm publish the new tarball.
   • Mirror the version into server.json.
   • Run mcp-publisher publish against the MCP registry.

3. Commit the server.json bump.

If you only want one side:

• make publish for npm only.
• make publish-mcp for the MCP registry only (server.json is always re-synced from package.json first).

mcp-publisher must be on PATH (brew install mcp-publisher or follow the installation docs).

Related

• mockzilla.org - hosted API simulation, per-PR mock URLs, GitHub Actions integration
• mockzilla/mockzilla - the core open-source API mock server
• Documentation - full usage guide for portable and codegen modes

License