mpx-api

We think Postman is bloated. This is API testing without the 500MB Electron app.

npm i -g mpx-api

What it does

Send HTTP requests, validate responses, spin up mock servers, manage collections. All from the terminal.

HTTP Requests

GET, POST, PUT, DELETE, PATCH — all the methods you need. Headers, query params, JSON bodies. One command, zero GUI.

YAML Collections

Define API test suites in simple YAML files. Variables, assertions, sequential requests. Git-friendly and shareable.

Mock Servers

Spin up mock endpoints in seconds. Test frontend code before the backend exists. Define responses in YAML.

Request Chaining

Use response data from one request in the next. Extract tokens, IDs, or any JSON value. Build complex workflows.

Assertions

Validate status codes, headers, response bodies. Fail fast on unexpected API changes. Perfect for CI/CD pipelines.

AI-Native

MCPMCP (Model Context Protocol) — lets AI assistants like Claude and GPT use CLI tools directly. server mode, --json output, --schema discovery. Tell your AI "test this API" and it just works.

Quick GET request

$ mpx-api GET https://api.github.com/users/octocat --json

{
  "login": "octocat",
  "id": 583231,
  "name": "The Octocat",
  "company": "@github",
  "blog": "https://github.blog",
  "location": "San Francisco",
  "public_repos": 8
}

✓ Status: 200 OK
✓ Response time: 142ms

POST with JSON body

$ mpx-api POST https://httpbin.org/post \
  --header "Content-Type: application/json" \
  --body '{"name": "test", "value": 123}'

✓ Status: 200 OK
✓ Content-Type: application/json
✓ Response contains "name": "test"

Run a collection

$ mpx-api run api-tests.yml

Running collection: User API Tests
✓ GET /users - 200 OK (98ms)
✓ POST /users - 201 Created (142ms)
✓ GET /users/123 - 200 OK (87ms)
✓ PUT /users/123 - 200 OK (156ms)
✓ DELETE /users/123 - 204 No Content (91ms)

5/5 tests passed in 574ms

Spin up a mock server

$ mpx-api mock --port 3000 mock-spec.yml

Mock server running at http://localhost:3000

Endpoints:
  GET  /users         → Returns user list
  GET  /users/:id     → Returns user by ID
  POST /users         → Creates new user
  PUT  /users/:id     → Updates user
  DELETE /users/:id   → Deletes user

Press Ctrl+C to stop

Free vs Pro

Feature	Free	Pro
HTTP requests (GET, POST, etc.)	✓	✓
YAML collections & assertions	✓	✓
JSON output & MCP server	✓	✓
Requests per day	50	Unlimited
Mock server endpoints	5	Unlimited
Request chaining	—	✓
Performance testing	—	✓
OpenAPI/Swagger import	—	✓

View on GitHub → View on npm → Documentation →

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