Simulate any API.
Ship integrations faster.

Point Ghostbox at any API with public documentation and get a fully stateful sandbox with realistic mock data — in minutes. No credentials, no rate limits, no side effects. Built for your code and your AI agents.

Get Started FreeRead the Docs

Two paths, same result. Pick whichever fits your workflow.

Swap the base URL
stripe-client.ts
const stripe = new Stripe(apiKey, {
-  // default: api.stripe.com
+  host: 'stripe.ghostbox.dev'
});
Or use the CLI
terminal
$ npx create-ghostbox@latest

$ npx ghostbox add stripe # instant
$ npx ghostbox add hubspot # generates from docs
$ npx ghostbox search payments

Ghostbox isn't limited to a handful of pre-built sandboxes. Point us at any API's documentation — OpenAPI specs, HTML reference pages, developer guides — and we generate a full sandbox with working endpoints, realistic data shapes, proper validation, and correct ID formats.

1

Search

Find a sandbox in the community registry, or request a new one

2

Generate

We analyze the docs and build a full stateful simulation automatically

3

Use

Same SDK, same code — just point at your-api.ghostbox.dev and ship

Most test environments return static JSON. Ghostbox runs a full stateful simulation with realistic mock data — proper IDs, correct field types, working cross-resource relationships, and native pagination styles. Not an approximation. A simulation.

Stateful sessions

Create a customer, then retrieve it. State persists across requests within a session — just like the real API.

Accurate response shapes

Every response matches the real API schema: field names, types, nesting, and pagination — all spec-accurate.

Error simulation

Inject rate limits, auth failures, and validation errors on demand with a single header. Test every edge case.

Magic values

Trigger specific behaviors with special values: bounce@resend.dev for bounces, 4000000000000002 for card declines.

Correct pagination

Cursor-based pagination for Stripe, page-based for Resend, offset for PostHog — each sandbox matches its API.

Isolated per key

Every API key gets its own sandbox with its own state. Your test data never leaks to other users or sessions.

Built for AI agents

Agents that call APIs need sandboxes that are deterministic, stateful, and schema-accurate. Ghostbox gives them that — a safe environment to operate without touching production systems or burning through real API credits.

  • MCP server

    Agents discover and interact with sandboxes through the Model Context Protocol. Standard tooling, zero custom wiring.

  • CLI & skills

    ghostbox add, ghostbox search — structured output designed for scripts and agent toolchains.

  • Safe by default

    No real credentials, no real charges, no side effects. Sandbox keys are obviously non-production — agents operate freely.

mcp.json
{
  "mcpServers": {
    "ghostbox": {
      "url": "https://mcp.ghostbox.dev",
      "headers": {
        "Authorization": "Bearer sandbox_test_..."
      }
    }
  }
}

Your production integration code runs unmodified against Ghostbox. No test doubles to maintain.

Before — real API, real problems
const stripe = new Stripe(
  process.env.STRIPE_SECRET_KEY
);

const customer = await stripe
  .customers.create({
    email: 'test@example.com'
  });

// Real charges. Real rate limits.
// Real problems in staging.
After — same code, safe sandbox
const stripe = new Stripe(
  process.env.STRIPE_SECRET_KEY,
  { host: 'stripe.ghostbox.dev' }
);

const customer = await stripe
  .customers.create({
    email: 'test@example.com'
  });

// Same SDK. Same code path.
// Zero charges. Zero side effects.

Free tier. 1,000 requests/month. No credit card required. Start simulating APIs in under a minute.

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