The Powerduck Blog
Product updates, engineering notes, and guides for designing, debugging, testing, mocking, and serving MCP tools from one OpenAPI spec.
Browse the guidesQuick answer: A static API reference tells a developer what an endpoint is, and an interactive playground lets them find out what it does, and the difference shows up the
Read articleQuick answer: OAuth looks solved until a token expires mid-session, and the failure is almost always in how refresh tokens are stored and coordinated rather than in the initial login.
Read articleQuick answer: Testing a WebSocket by hand in a collection client tells you the server accepts a connection and echoes a message, but it does not give you a repeatable
Read articleQuick answer: A public MCP registry is a great home for a general-purpose tool you want strangers to discover, but it is the wrong place to expose an internal API
Read articleQuick answer: Agents love to fire several API calls in parallel because it feels fast, and for independent reads it is, but parallel writes against the same resource are a
Read articleQuick answer: Importing a Postman collection is a useful migration shortcut and a dangerous thing to trust blindly, because the importer faithfully recreates requests while silently dropping or flattening the
Read articleQuick answer: Query parameters that are arrays or nested objects are one of the most common silent contract mismatches, because the OpenAPI name and type say nothing about how the
Read articleQuick answer: Most OpenAPI generators map format: date-time to a plain string rather than a real date object, which is convenient for the type system and dangerous for the application:
Read articleQuick answer: A blocking MCP tool that wraps a long-running operation is a design error that shows up as a hung agent: the model waits on a single call that
Read articleQuick answer: Snapshot tests are cheap to write and expensive to trust when they lock down an entire response that includes volatile fields like timestamps, generated ids, and request echoes.
Read articleQuick answer: Pagination is where mock-based tests quietly get flaky, because most real endpoints don't return a fixed set of rows, and a mock that hands back the
Read articleQuick answer: A 404 that looks like a missing resource is often a routing problem in disguise: the client dropped a base path prefix, or a trailing slash changed which
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