FetchSandbox

What is FetchSandbox?

FetchSandbox is a verification layer for API integrations written by AI coding agents. It runs your agent's code against stateful sandboxes for Stripe, Twilio, Resend, and other APIs, then breaks things on purpose with duplicate webhooks and failed requests. Every run ends with a clear pass or fail verdict and receipt.

Top Features:

• Failure simulation: duplicate webhooks, reorder events, fire stale events, and trigger rate limits.
• Stateful sandboxes: orders and payments persist across calls instead of static mock replies.
• IDE access: an MCP server and CLI plug into Cursor and Claude Code.

Use Cases:

• Payment testing: check Stripe checkout and invoice webhooks before real money moves.
• Agent code checks: prove that integration code from coding agents survives retries and failures.
• Internal APIs: upload an OpenAPI spec to get a sandbox for internal services.

Who Can Use FetchSandbox?

• Backend developers: test webhook handlers and async flows without burning real API quota.
• AI-first builders: check code generated in Cursor or Lovable before it reaches production.
• Platform teams: gate pull requests in CI with repeatable integration checks and receipts.

Pricing

• Free ($0 per developer): 500 runs and 5 fixes monthly, with MCP and CLI access.
• Pro ($200 per workspace monthly): 10,000 runs, 100 fixes, receipts, run history, and a CI gate.
• Team ($999 per month): 10 workspaces, unlimited runs, 500 fixes, and 5 custom APIs.

Pros and Cons

Pros:

• Repeatable results: the same scenario gives the same outcome on every single run.
• No live keys: tests run without production credentials or spending real provider quota.
• In the IDE: results show up where you code instead of a separate dashboard.

Cons:

• Steep jump: the jump from free to Pro costs $200 per workspace monthly.
• Catalog limits: ready-made scenarios cover popular APIs, while niche services need spec uploads.
• Early stage: a young product, so community guides and tutorials are still scarce.

FAQs:

1) Do I need real API keys?

No, sandboxes mimic provider behavior, so production credentials stay untouched.

2) Which IDEs work?

It runs in Cursor, Claude Code, Codex, Lovable, and Windsurf.

3) Is there an enterprise plan?

Yes, custom pricing adds single sign-on, audit logs, and self-hosting.

4) How is it unlike Postman mocks?

Postman mocks stay static, while these sandboxes keep state across calls.

5) Can I test internal APIs?

Yes, upload an OpenAPI 3 spec to provision a full sandbox.