I am working on my own agent implementation (https://usehax.dev/), and I can praise OpenRouter for being seemingly the only provider endpoint that actually gives proper API for gathering available models and their capabilities (context length, image support, pricing, etc), reports exact routing details and total cost in the response, and provides an endpoint for obtaining current available credits (for "/usage"-like command). So for OpenRouter specifically I could deliver a really good experience out-of-the-box (always fresh models and metadata, exact pricing, etc).

You would think that these things would be standard fare, but they really are not. Other providers need metadata from a separate catalog, don't report pricing, don't really report available credits / usage either.

So yes, OpenRouter does have a good DevEx.