Swagger matters because interactive API docs reduce integration mistakes and expose contract drift. It gives builders a precise word for the thing they are changing, debugging, reviewing, or shipping.
ELI5
Think of Swagger as a rule for how information is shaped and checked. It gives one small job a clear name so the whole app is easier to understand.
In practice
Use it when data crosses forms, APIs, databases, or AI outputs. In practice, name the owner, input, output, failure mode, and proof before relying on Swagger.