Top 5 API Bugs I Catch With Postman Before Writing a Single Test

Before I automate anything, I spend time in Postman finding the bugs that automation would otherwise take longer to surface. Here are the five that show up most often.

1. Inconsistent status codes on validation errors

A lot of APIs return 200 even when the request body is invalid, pushing the real error into the response payload instead. This breaks the contract your automated assertions rely on.

2. Pagination that silently drops the last page

Test the last page explicitly — a common off-by-one bug returns an empty array instead of the final partial page.

Quick check in Postman

{
  "page": 999,
  "limit": 10
}

If this returns 200 with an empty array instead of 404 or a clear "no more results" signal, flag it early.

3. Auth tokens that never expire

4. Missing rate limiting on write endpoints

5. Case-sensitive query parameters

Small thing, but ?Status=active silently failing while ?status=active works is a real bug users will hit.