Mockbird
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Hosted mock-API MCP server: agents create live REST/GraphQL mock APIs, import OpenAPI/CSV/db.json, seed fake data, query and write records — free, no auth, stateless Streamable HTTP.
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An MCP mock-API server: let your coding agent spin up the backend
Coding agents keep hitting the same wall humans do: the frontend they're writing needs an API that doesn't exist yet. The usual agent workarounds are all bad — hardcode JSONPlaceholder (fixed schema, fake writes), generate an MSW handler file (more code to maintain, only exists inside the test process), or scaffold an Express server (now your "mock" has a package.json, a port, and a lifecycle).
# Claude Code claude mcp add --transport http mockbird https://mockbird.mockbird.workers.dev/mcp # Cursor / Windsurf / any client that reads mcp.json { "mcpServers": { "mockbird": { "url": "https://mockbird.mockbird.workers.dev/mcp" } } } # VS Code code --add-mcp '{"name":"mockbird","type":"http","url":"https://mockbird.mockbird.workers.dev/mcp"}'
The transport isstateless Streamable HTTP(spec 2025-06-18; older 2025-03-26 and 2024-11-05 clients work too). No session juggling, no SSE requirement, no server to install — it's the same Cloudflare Worker that serves the mocks. Mockbird is also listed in the official MCP Registry asdev.workers.mockbird.mockbird/mockbird.
Every tool dispatches through thesamecode paths as the public HTTP API, so therequest inspector, daily caps, and anonymous per-IP limits apply identically. TheadminKeyreturned bycreate_projectis shown once — well-behaved agents save it into the project's.env.
"Create an ecommerce mock API with Mockbird and point this app's .env at it. Then write a Playwright test that checks the empty-cart state using a snapshot."
A capable agent will: callcreate_projectwithpreset: "ecommerce"(one call — products, orders, customers, reviews, all seeded), writeVITE_API_URL=<baseUrl>into.env, callsnapshotswithaction: "save"after emptying the fixture data it needs, and pin that scenario in tests viamock_snapshot=<name>inquery_recordsparams — the samesnapshot pinninghumans use, no restore races between parallel workers.
The important part:the mock itself stays plain HTTP. The code your agent writes ships with a working URL — you can curl it, open it in a browser, hand it to a teammate, or run CI against it after the agent session ends. The mock isn't trapped inside the agent's tool sandbox.
No MCP client? It's just JSON-RPC over POST
You can drive the whole thing from curl — useful for debugging what your agent sees:
# list the tools curl -s -X POST https://mockbird.mockbird.workers.dev/mcp -H 'content-type: application/json' \ -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' # call one: the shared demo project's index curl -s -X POST https://mockbird.mockbird.workers.dev/mcp -H 'content-type: application/json' \ -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{ "name":"project_info","arguments":{"project":"demo"}}}' # query with projection + pagination curl -s -X POST https://mockbird.mockbird.workers.dev/mcp -H 'content-type: application/json' \ -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{ "name":"query_records","arguments":{"project":"demo", "resource":"products","params":{"_limit":2,"select":"name,price"}}}}'
All three run against the live server right now — the last one returns two products with justid,name,price.
Honest answer: agentscanalready use Mockbird with plain HTTP — that's why/llms.txtexists, and agent traffic does arrive that way. MCP adds three things:discovery(the agent finds typed tools with descriptions instead of reading docs into context),fewer tokens(tool results are trimmed and capped at 50 KB, with a hint to useselect/_limitwhen truncated), andfewer mistakes(input schemas encode the gotchas — field types, which calls need the adminKey — so the agent doesn't learn them by 400ing). If your agent runs fine on raw HTTP, nothing forces the switch.
Limits, honestly: tool calls share the project's 10,000 requests/day cap and anonymous project creation is limited to 30/IP/day (the MCP server forwards your real client IP for caps — one shared egress IP for a big agent fleet will hit it). Responses are JSON only, no streaming. The server is stateless, so clients that require session-id handshakes fall back to sessionless mode per spec. And the data is mock-grade: this is for building against an API shape, not for storing anything you care about. Full reference in thedocs.
More guides:deterministic test data·mock server from an OpenAPI spec·testing loading & error states·free mock API tools compared.Create your API →
⚡Skip the terminal:this link creates a live, seeded e-commerce backend (products, orders, customers, reviews) in the dashboard— real URL, data browser already open, no signup. Orimport your own OpenAPI spec, db.json, CSV, Postman collection, or HARand mock your exact shapes.
This is a web browser that enables your coding agent, such as Claude Code, to visit websites on your behalf and assist you in identifying bugs or creating UI test cases.
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