Applications built around Anthropic Messages can use POST /v1/messages. Include these headers: 
Authorization: Bearer YOUR_API_KEY
anthropic-version: 2023-06-01
Content-Type: application/json

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Parameters

ParameterRequiredMeaning
modelYesExact Claude model ID available to your key.
messagesYesCurrent input and conversation history.
max_tokensYesMaximum generated output length; must be at least 1.
systemNoSystem prompt.
thinkingNoThinking configuration, only where supported by the selected model.
Preserve the Messages request structure when moving an existing Anthropic-compatible application. Do not send an OpenAI messages request with incompatible fields unchanged to this endpoint. Claude Code setup uses the origin https://infistar.ai, without /v1; the client adds the request path itself.