Authentication
Send your API key on every request.
Every /v1 request needs an API key, sent either way:
Authorization: Bearer sk-si-...x-api-key: sk-si-...x-api-key is what Anthropic SDKs send; Authorization: Bearer is what OpenAI SDKs send. Both work on every endpoint.
A missing, revoked or unknown key returns 401 with code invalid_api_key.
Projects and keys
Section titled “Projects and keys”Keys belong to projects in the dashboard. Every key spends from your account balance; you can give a key a monthly spend limit, after which its requests return 402 key_limit_exceeded until the next month.
Keep keys server-side. Anyone holding a key can spend your balance; revoke a leaked key from the dashboard right away.