# Messages

POST /v1/messages: Anthropic format for Claude Code and similar clients.

`POST https://ai.sivcloud.com/v1/messages` uses the Anthropic Messages format. Claude Code and the Anthropic SDK use it.

```bash
curl https://ai.sivcloud.com/v1/messages \
  -H "x-api-key: $SIVCLOUD_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "deepseek-v4.1-flash",
    "max_tokens": 256,
    "messages": [{"role": "user", "content": "Hello"}]
  }'
```

The `Authorization: Bearer` header is also accepted.

## Response

```json
{
  "type": "message",
  "role": "assistant",
  "model": "deepseek-v4.1-flash",
  "content": [{"type": "text", "text": "Hello!"}],
  "stop_reason": "end_turn",
  "usage": {"input_tokens": 20, "output_tokens": 3, "cache_read_input_tokens": 0}
}
```

`cache_read_input_tokens` is the input read from cache, and `cache_creation_input_tokens` is what was written to cache. See [Cache](https://sivcloud.com/en/docs/cache/).

## Count tokens

`POST https://ai.sivcloud.com/v1/messages/count_tokens` counts the input tokens of a Messages request without creating a message. The body is the same as `/v1/messages`; `system`, `messages` and `tools` are all counted.

```bash
curl https://ai.sivcloud.com/v1/messages/count_tokens \
  -H "x-api-key: $SIVCLOUD_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "deepseek-v4.1-flash", "messages": [{"role": "user", "content": "Hello"}]}'
```

```json
{"input_tokens": 9}
```

The number is a local estimate and can differ slightly from `usage` in the response. The call is free: it does not touch your balance or allowance and does not appear in the usage log. An API key is still required.

## Good to know

- `max_tokens` is required, as in the Anthropic API. The cost reserve is computed from it.
- Not every model opens this endpoint. The Models page in the console marks the endpoints of each model.
- Streaming uses `"stream": true`. See [Streaming](https://sivcloud.com/en/docs/streaming/).
- Claude Code setup is on the [Claude Code](https://sivcloud.com/en/docs/tools/claude-code/) page.