Messages

Anthropic-compatible messages endpoint. Use this if you prefer the Anthropic API format.

POST/v1/messages

Request Parameters

Parameter	Type	Required	Description
`model`	string	Yes	The model to use (e.g. "claude-sonnet-4-20250514", "gpt-4o")
`messages`	array	Yes	Array of message objects. Each message has a role and content (string or content blocks)
`max_tokens`	integer	Yes	Maximum number of tokens to generate
`system`	string	No	System prompt to guide the model's behavior
`stream`	boolean	No	If true, returns a stream of server-sent events. Default: false

Request Example

curl https://api.osiris.ai/v1/messages \
  -H "Authorization: Bearer sk-osiris-YOUR_KEY" \
  -H "Content-Type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-20250514",
    "max_tokens": 1024,
    "system": "You are a helpful assistant.",
    "messages": [
      {
        "role": "user",
        "content": "What is the capital of France?"
      }
    ]
  }'

Content Blocks

Messages can use content blocks instead of plain strings. This allows structured content like text blocks:

Content blocks format

{
  "model": "claude-sonnet-4-20250514",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "Describe what you see in this image."
        }
      ]
    }
  ]
}

Response Format

The response follows the Anthropic message format with content blocks:

Response

{
  "id": "msg_abc123",
  "type": "message",
  "role": "assistant",
  "model": "claude-sonnet-4-20250514",
  "content": [
    {
      "type": "text",
      "text": "The capital of France is Paris."
    }
  ],
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 25,
    "output_tokens": 12
  }
}

Streaming

When stream: true, the response is delivered as SSE events in the Anthropic streaming format:

SSE stream format

event: message_start
data: {"type":"message_start","message":{"id":"msg_abc123","type":"message","role":"assistant","model":"claude-sonnet-4-20250514","content":[],"stop_reason":null,"usage":{"input_tokens":12,"output_tokens":0}}}

event: content_block_start
data: {"type":"content_block_start","index":0,"content_block":{"type":"text","text":""}}

event: content_block_delta
data: {"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"Hello"}}

event: content_block_delta
data: {"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"!"}}

event: content_block_stop
data: {"type":"content_block_stop","index":0}

event: message_delta
data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"output_tokens":2}}

event: message_stop
data: {"type":"message_stop"}

Streaming Request

curl https://api.osiris.ai/v1/messages \
  -H "Authorization: Bearer sk-osiris-YOUR_KEY" \
  -H "Content-Type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-20250514",
    "max_tokens": 1024,
    "stream": true,
    "messages": [{"role": "user", "content": "Hello!"}]
  }'