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Messages API

POST /v1/messages — the Anthropic-format endpoint: parameters, response shape and examples.

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The endpoint every Anthropic-compatible client uses, including Claude Code and the official SDKs.

EndpointPOST https://aiprimetech.io/v1/messages

Authx-api-key: sk-...

Version headeranthropic-version: 2023-06-01

Content typeapplication/json

Request body

Field	Type	Required	Description
`model`	string	yes	Model id, exactly as listed by `/v1/models`
`messages`	array	yes	Alternating user / assistant turns, oldest first
`max_tokens`	integer	yes	Maximum output tokens. Generation stops here.
`system`	string or array	no	Top-level system prompt. Not a message role.
`temperature`	number	no	0–1. Omit for the model default.
`top_p`	number	no	Nucleus sampling. Use this or temperature, not both.
`stop_sequences`	array	no	Strings that halt generation when produced
`stream`	boolean	no	true for server-sent events
`tools`	array	no	Tool definitions — see Tool use
`metadata`	object	no	Passed through; `user_id` is useful for your own attribution

Example

curl https://aiprimetech.io/v1/messages \
  -H "x-api-key: $CLAUDEAPIKEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-sonnet-4-6",
    "max_tokens": 1024,
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Response

{
  "id": "msg_01ABC...",
  "type": "message",
  "role": "assistant",
  "model": "claude-sonnet-4-6",
  "content": [{"type": "text", "text": "..."}],
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {"input_tokens": 9, "output_tokens": 12}
}

Field	Description
`content`	Array of blocks. Text blocks carry `type: text` and a `text` field; tool calls carry `type: tool_use`.
`stop_reason`	`end_turn`, `max_tokens`, `stop_sequence` or `tool_use`
`usage.input_tokens`	Billed input, including the full resent history
`usage.output_tokens`	Billed output — typically 4–5× the input rate

System prompts

{
  "model": "claude-sonnet-4-6",
  "max_tokens": 1024,
  "system": "You are a terse assistant. Answer in at most two sentences.",
  "messages": [{"role": "user", "content": "Explain HTTP caching."}]
}

A stable system block is the ideal target for prompt caching — it is identical on every call, so it can be read from cache at a fraction of the input price.

Multimodal input

Image blocks use the standard Anthropic shape — see Vision.

StreamingToken-by-token output Tool useFunction calling ErrorsFailure modes