If the expectation is that the client opens a URL with a specific program, such as a web browser or PDF viewer, then it's acceptable to end a URL with a file extension. Otherwise, per REST API naming ...

Google announced the launch of a new URL Inspection API which allows an outside app to interact with Google’s search console and provide URL inspection data. The new API access will help SEOs ...

The API will return indexed information from the URL Inspection Tool including index status, AMP, rich results, and mobile usability. You can see the full list of responses over here in the API docs.