Why a CORS Preflight OPTIONS Request Returns 401
The browser's preflight carries no credentials, so an auth layer that meets it first returns 401.
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API engineering, from the spec out
Product updates, engineering notes, and guides for designing, debugging, testing, mocking, and serving MCP tools from one OpenAPI spec.
Browse the guides503 Service Unavailable: Why It Happens and How to Back Off
A temporary "not right now" from the server, and the client job is to wait well.
Read article502 Bad Gateway vs 504: How to Tell Them Apart
Same gateway layer, two different failures, and two different fixes.
Read articleDebugging 416 Range Not Satisfiable
A 416 is a mismatch between the byte range and the resource size.
Read articleDebugging 411 Length Required with Chunked Input
A 411 is a framing problem, not a body-content problem.
Read articleDebugging 423 Locked Resource
A 423 is a resource held under a lock, not a bad request.
Read articleDebugging a 400 Caused by a Trailing Comma in JSON
JSON has no trailing commas, even when the payload looks right.
Read articleWhy a Green Build Is Not Enough for a Confident Merge
The build is a gate, not a verdict on behavior.
Read articleWhen to Trust the Recommendation and When to Probe
The recommendation is a lead, not an order.
Read articleWhat to Include in a Review Context Package
Include connected context, not the whole codebase.
Read articleVerify an API Change With a Real Request, Not a Hunch
A hunch predicts; a request confirms.
Read articleValidating a Business Flow After an Agent Edit
Verify the whole sequence, not just one endpoint.
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