Count tokens

Anthropic's token count for a Messages request is not served yet. The route exists so that a client gets a clear answer: 404 not_found_error with the code route_not_available, in the Messages route's error shape. Every Messages answer carries the exact counts in its usage, and Claude Code estimates its context itself when the count is not served.

00000000000000000000000000000000000000001{2  "type": "error",3  "error": {4    "type": "not_found_error",5    "message": "POST /v1/messages/count_tokens is not served yet; each answer's usage carries the exact counts.",6    "code": "route_not_available"7  },8  "request_id": "req_..."9}

Any other method on the path is 404 method_not_allowed with Allow: POST.