FetchSandbox MCP lets agents test against recorded real provider behavior, not mocks

Common_Dream9420 · reddit · 2026-09-02

A dev team found in production that agents pass every mock test yet fail on the first live webhook — mocks are behavioral simulations while real providers have memory, with differing auth failures, 429s, and retry cycles. They built FetchSandbox MCP so agents run the full loop against a twin of the actual service provider, using recorded real response patterns rather than guessed simulations. The author asks the community: are you mocking at all, or testing straight against staging?

Related event: FetchSandbox: Testing Agents Against Real Vendor Behavior(2 posts)→

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