The Powerduck Blog
Product updates, engineering notes, and guides for designing, debugging, testing, mocking, and serving MCP tools from one OpenAPI spec.
Browse the guidesTypeScript clients from OpenAPI split into three camps: types-only, fetch wrappers, and full SDK generators. They differ in runtime weight, enum handling, and how they break on spec changes. Here is how to choose and wire the winner into CI without generated-code sprawl.
Read articleGenerated screens fail on limit versus pageSize, data.records versus data.items, cents versus dollars. The fix is not a better prompt; it is letting the agent query the real contract and verify against real responses.
Read articleEvery new coding assistant starts with the same ritual: paste the docs, explain the fields, warn about stale versions. A local spec served over MCP makes that context permanent.
Read articleMSW intercepts requests inside the browser and shines in component tests; Prism serves a spec over HTTP and validates contracts; spec-driven workspaces add journeys and streams. Here is where each belongs and how teams combine them without maintaining three sets of fixtures.
Read articleAI across the entire API lifecycle, drafting operations from cURL or Postman, generating tests, explaining failures, with a review-and-revert model and a local-first guarantee: your file stays the source of truth.
Read articleWebhooks are reverse APIs: your server is the client, so the documentation has to cover payloads, delivery ordering, retries, signature verification, and endpoint registration. OpenAPI 3.1 made webhooks top-level citizens — here is a complete, consumer-ready webhook definition.
Read articleA booking app built from one prompt can pass every visual check and still fail on time zones, double bookings, and stale cancel responses. Teams need a contract both people and tools can query, change, and verify.
Read articleA request that runs is the start of a handoff, not the end of one. Import the curl, capture the missing context, and promote what you learned back into the specification.
Read articleWebSocket testing breaks every habit from REST: the handshake is HTTP but everything after is framed and bidirectional, auth happens at upgrade time or immediately after, and correctness means message sequences. Here is a practical testing workflow from wscat to CI scenarios.
Read articleReal systems are multi-protocol: REST at the edge, WebSockets for events, gRPC between services, GraphQL at the gateway. Powerduck debugs all of them from the same workspace and the same spec.
Read articleSSE looks like HTTP until you try to test it: the connection stays open, events have names and ids, heartbeats hide disconnects, and ordinary API clients hang. Here is how to test streams with curl, what Postman does and does not do, and how to make SSE scenarios repeatable from an OpenAPI spec.
Read articleEvery API invents an error envelope once; integrations then handle a bespoke format per vendor. RFC 9457 Problem Details is the machine-readable standard, and it extends cleanly to validation and multi-error responses.
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