Which model should I name?
Model ids carry their provider, the set of callable models is a live fact rather than a documented list, and models arrive and retire on their providers’ schedules rather than ours.Models
Id forms, how to discover what your key can call, and how a rate is expressed.
Model capabilities
Which features a given model supports, and how to ask before you rely on one.
Model lifecycle
How a model appears, changes, and goes away, and what your code sees when it does.
What can I put in a request?
These are the request-shaping features. Each is the OpenAI parameter you already know, with a note on what differs when a router rather than a single provider is serving it.Streaming
Server-sent events, the usage comment before the final line, and mid-stream failure.
Tool calling
Passing tools through, and what a model that cannot call them does instead.
Structured outputs
JSON mode and schema-constrained responses, and which models honour them.
Image inputs
Multi-modal messages, and the refusal a text-only model returns.
Reasoning
Reasoning-model behaviour, the tokens it spends, and how they are billed.
Prompt caching
Where caching happens, who controls it, and what it does to a request’s cost.
What happens when something goes wrong?
Routing is the part of the product you did not have when you called a provider directly, so it is the part worth reading before an incident rather than during one.Routing profiles
How a request reaches a provider, and what you can say about that choice.
Bring your own key
Serving a model on your own provider credential instead of ours.
Errors
The error envelope, the closed set of types, and what each one asks you to do.