FetchSandbox: import any OpenAPI spec, get a mock API in 5 seconds with shareable receipts
Common_Dream9420 · reddit · 2026-09-21
FetchSandbox is a sandbox layer for third-party APIs. Its MCP server (npx fetchsandbox-mcp) lets agents import any OpenAPI spec and spin up a fully running mock in 5 seconds, run step-by-step workflows, fire named failure scenarios (rate limits, webhook retries, payment declined, flaky webhooks), and get a public receipt URL showing every request, response and webhook in one timeline.
The author's typical loop in Cursor and Claude Code: the agent writes a Stripe integration, runs the acceptpayment workflow against FetchSandbox, inspects the receipt, and catches a missing idempotency key before touching the real API. 32 specs are live today including Stripe, Twilio, Resend, Clerk, PayPal, Notion and GitHub. Receipt URLs are public and shareable — paste one in a PR as actual proof the integration works, not just "ran fine locally."
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