Short answer: Both tools send a request and show the response. The difference is that a contract-first studio verifies the response against the schema and flags the field that is wrong, while a collection tool shows the body and moves on. If you want to catch undeclared properties and type drift, you need the contract check.

What a response view tells you

A status and a body prove the server answered. They do not prove the answer is valid. The field that is wrong is often the one nobody is looking at, which is why a visible 200 and a real contract violation coexist.

What contract verification examines

ConditionResponse viewContract check
Undeclared propertyShown, not flaggedFlagged
Missing required fieldNot noticedFlagged
Type driftNot noticedFlagged
Valid responseShownConfirmed

The failure that matters

The dangerous bug is a response that looks fine and violates the API: a new property the client was not told about, or a field that changed type. The contract check examines the whole response, so it does not depend on a human reading every field.

How to use both

Send and inspect requests in whichever tool you prefer, and run the contract check to prove conformance. The view and the verification answer different questions.

This is part of the Powerduck vs Hoppscotch comparison. Next, read migrating collections.