Anthropic API
Use an Anthropic API key for strong long-form writing.
In short
The Anthropic engine calls the native Messages API with your own API key. It is a good default for drafting and for the literature method, where long, careful writing matters.
1Get a key
Create an API key in the Anthropic console.
2Add it
Settings → AI engines → Anthropic: paste the key and Save, then pick a model for the cheap and strong tiers in Models.
For technical users
Wire: POST /v1/messages with x-api-key and anthropic-version: 2023-06-01, streamed over SSE; models come from GET /v1/models (paginated). Leading system messages become the system parameter and a later system message (a repair instruction) is folded into the next user turn. Errors map to the shared codes, including 429 with retry-after and 529 overloaded. The key uses the same secret store as every other engine. No credit is shown (only OpenRouter reports it).