Rest Api fetch additional data of entity

Question

When we need to fetch a sub resource of an entity, the best practice is to do:

 GET - todos/:id

But I can't find any information about best practices regarding fetching additional data about this resource. What is the best practice if I want to fetch the todos metrics data?

GET - todos/metrics

Is this the correct approach?

If so, it will not collide with todos/:id?

Answer 1

There's no "one right" way to handle this. Your suggestion is appropriate, but can be confused for a potential ID "metrics". You can also use query parameters:

GET - todos/?metrics

or use a placeholder:

GET - todos/-/metrics

or, treat the metrics as a resource of it's own, so you actually are getting metrics, about the todos resource:

GET - metrics/todos

Anything here would be fine, so long as you're consistent across your resources.