Anthropic Messages Protocol

curl https://api.poixe.com/v1/messages \
  -H "Content-Type: application/json" \
  -H 'anthropic-version: 2023-06-01' \
  -H "X-Api-Key: $POIXE_API_KEY" \
  -d '{
        "max_tokens": 1024,
        "messages": [
          {
            "role": "user",
            "content": "Hello!"
          }
        ],
        "model": "claude-sonnet-4-5-20250929",
        "stream": false
      }'

{
  "model": "claude-sonnet-4-5-20250929",
  "id": "msg_019SV1gQjKXteTibBnxT9rN3",
  "type": "message",
  "role": "assistant",
  "content": [{ "type": "text", "text": "Hello! How can I help you today?" }],
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 9,
    "cache_creation_input_tokens": 0,
    "cache_read_input_tokens": 0,
    "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 0
    },
    "output_tokens": 12,
    "service_tier": "standard"
  }
}

event: message_start
data: {"type":"message_start","message":{"model":"claude-sonnet-4-5-20250929","id":"msg_01CMBTNth2rdhkVuTvzM6VDq","type":"message","role":"assistant","content":[],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":9,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":0},"output_tokens":8,"service_tier":"standard"}}}

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! How can I help you today"}}

....

event: ping
data: {"type": "ping"}

....

event: message_delta
data: {"type":"message_delta","delta":{"stop_reason":"end_turn","stop_sequence":null},"usage":{"input_tokens":9,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"output_tokens":12}}

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

curl https://api.poixe.com/v1/messages \
  -H "Content-Type: application/json" \
  -H 'anthropic-version: 2023-06-01' \
  -H "X-Api-Key: $POIXE_API_KEY" \
  -d '{
        "max_tokens": 1024,
        "messages": [
          {
            "role": "user",
            "content": "Hello!"
          }
        ],
        "model": "claude-sonnet-4-5-20250929",
        "stream": false
      }'

{
  "model": "claude-sonnet-4-5-20250929",
  "id": "msg_019SV1gQjKXteTibBnxT9rN3",
  "type": "message",
  "role": "assistant",
  "content": [{ "type": "text", "text": "Hello! How can I help you today?" }],
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 9,
    "cache_creation_input_tokens": 0,
    "cache_read_input_tokens": 0,
    "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 0
    },
    "output_tokens": 12,
    "service_tier": "standard"
  }
}

event: message_start
data: {"type":"message_start","message":{"model":"claude-sonnet-4-5-20250929","id":"msg_01CMBTNth2rdhkVuTvzM6VDq","type":"message","role":"assistant","content":[],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":9,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":0},"output_tokens":8,"service_tier":"standard"}}}

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! How can I help you today"}}

....

event: ping
data: {"type": "ping"}

....

event: message_delta
data: {"type":"message_delta","delta":{"stop_reason":"end_turn","stop_sequence":null},"usage":{"input_tokens":9,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"output_tokens":12}}

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

curl https://api.poixe.com/v1/messages \
  -H "Content-Type: application/json" \
  -H 'anthropic-version: 2023-06-01' \
  -H "X-Api-Key: $POIXE_API_KEY" \
  -d '{
        "max_tokens": 1024,
        "messages": [
          {
            "role": "user",
            "content": "Hello!"
          }
        ],
        "model": "claude-sonnet-4-5-20250929",
        "stream": false
      }'

{
  "model": "claude-sonnet-4-5-20250929",
  "id": "msg_019SV1gQjKXteTibBnxT9rN3",
  "type": "message",
  "role": "assistant",
  "content": [{ "type": "text", "text": "Hello! How can I help you today?" }],
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 9,
    "cache_creation_input_tokens": 0,
    "cache_read_input_tokens": 0,
    "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 0
    },
    "output_tokens": 12,
    "service_tier": "standard"
  }
}

event: message_start
data: {"type":"message_start","message":{"model":"claude-sonnet-4-5-20250929","id":"msg_01CMBTNth2rdhkVuTvzM6VDq","type":"message","role":"assistant","content":[],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":9,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":0},"output_tokens":8,"service_tier":"standard"}}}

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! How can I help you today"}}

....

event: ping
data: {"type": "ping"}

....

event: message_delta
data: {"type":"message_delta","delta":{"stop_reason":"end_turn","stop_sequence":null},"usage":{"input_tokens":9,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"output_tokens":12}}

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

POST https://api.poixe.com/v1/messages

This is the core chat protocol for Claude (Anthropic), supporting text, multimodal input, tool calling, and SSE streaming output. On this path, the system aligns with Anthropic’s field and event stream formats, so you can reuse existing Claude SDKs or request structures directly.

Authentication and request headers

Every request must carry an API key. We also recommend always sending anthropic-version to keep behavior stable.

string

required

Poixe API key. The format is X-Api-Key: YOUR_API_KEY (equivalent to x-api-key).

string

required

The Anthropic version number, for example: 2023-06-01.

string

required

Must be set to application/json.

Core request parameters

The following are the most commonly used and most general fields (enough to cover regular chat, tool calling, and streaming).

string

required

The model ID, for example: claude-sonnet-4-5-20250929.

object[]

required

The list of conversation messages.

Show messages[] fields

string

required

The role: user / assistant.

string or array

required

The message content. Usually a string; for multimodal or structured scenarios, you can use an array (content blocks).

integer

required

The maximum number of output tokens allowed for this generation.

boolean

default:"false"

Whether to enable SSE streaming output. When true, the response is text/event-stream.

number

Optional: sampling temperature. Lower values are more stable; higher values are more divergent (if omitted, the model default is used).

string

Optional: the system prompt (used to set the assistant’s overall behavior).

object[]

Optional: the list of tools (function/tool calling).

Show tools[] fields

string

required

Tool name

string

Tool description

object

Parameter schema (JSON Schema)

object

Optional: tool-calling strategy, for example {"type":"any"} (allows calling any tool).

Response structure and streaming events

For non-streaming requests, a message object is returned. For streaming requests, a series of SSE events is returned (message_start → content block events → message_delta → message_stop), and ping events may be interspersed.

string

Message ID, for example msg_xxx

string

Always message

string

Always assistant

object[]

The array of generated content, commonly [{ "type": "text", "text": "..." }].

string

The reason generation stopped. Common values: end_turn / max_tokens / stop_sequence / tool_use (and, in rare cases, pause_turn / refusal / model_context_window_exceeded, and so on).

string | null

The matched stop sequence string if one was hit; otherwise null.

object

Token usage statistics.

Show usage fields (common)

integer

Input tokens consumed

integer

Output tokens consumed

Official docs: Create a Message

View the complete parameters and examples for the Claude Messages API (including tools, multimodal input, and streaming events).

API Reference

Text APIs

System APIs

Anthropic Messages Protocol

Authentication and request headers

Core request parameters

Response structure and streaming events

Official docs: Create a Message

​Authentication and request headers

​Core request parameters

​Response structure and streaming events

Official docs: Create a Message

Authentication and request headers

Core request parameters

Response structure and streaming events