OpenAI Chat API

This platform provides a chat endpoint compatible with the OpenAI Chat Completions API.

This document is intended for client-side integrators and focuses on the public request path, authentication method, request parameters, and example payloads. Field names and JSON structure are kept as close as possible to the native OpenAI Chat Completions API.

Overview:

Endpoint: POST /v1/chat/completions
Capability type: chat / text generation
Response modes:
- When stream = false or omitted: standard JSON response
- When stream = true: text/event-stream SSE response
Protocol style: the request body follows the native OpenAI Chat Completions structure and does not wrap content in an extra input field

Current scope:

Covers only POST /v1/chat/completions
POST /v1/responses is also supported, but is documented separately at /docs/api-reference/text/openai-response-api
Does not cover other OpenAI endpoints such as embeddings, images, or audio

1. API Overview

HTTP method: POST
Request path: /v1/chat/completions
Content-Type: application/json
Response type:
- Non-streaming: application/json
- Streaming: text/event-stream

2. Authentication and Headers

Example headers:

Authorization: Bearer YOUR_REACH_API_KEY
Content-Type: application/json

At least one of Authorization or x-api-key must be provided.

Header details:

Header	Required	Description
`Authorization`	No	Platform API key in the format `Bearer sk-xxxxxx`
`x-api-key`	No	You can also pass the platform API key directly in this header
`Content-Type`	Yes	Must be `application/json`

3. Request Body

The request body follows the native OpenAI Chat Completions object structure:

{
  "model": "YOUR_MODEL_ID",
  "messages": [
    {
      "role": "user",
      "content": "Please introduce yourself in one sentence."
    }
  ],
  "temperature": 0.2,
  "stream": false
}

3.1 Top-Level Parameters

Field	Type	Required	Description
`model`	string	Yes	Model ID
`messages`	`array<object>`	Yes	Chat message list, at least one item
`temperature`	number	No	Sampling temperature
`top_p`	number	No	Nucleus sampling parameter
`n`	integer	No	Number of candidate results
`max_tokens`	integer	No	Maximum number of output tokens
`max_completion_tokens`	integer	No	New output token limit supported by some models
`stop`	`string` or `array<string>`	No	Stop sequences
`stream`	boolean	No	Whether to return SSE streaming output
`stream_options`	object	No	Additional streaming configuration such as `include_usage`
`tools`	`array<object>`	No	Tool definitions
`tool_choice`	string or object	No	Tool calling strategy
`parallel_tool_calls`	boolean	No	Whether parallel tool calls are allowed
`response_format`	object	No	Structured output configuration
`presence_penalty`	number	No	Penalty for topic novelty
`frequency_penalty`	number	No	Repetition penalty
`logit_bias`	object	No	Token bias configuration
`user`	string	No	End-user identifier

3.2 `messages` Parameter

Each message uses the following structure:

Field	Type	Required	Description
`role`	string	Yes	Role. Common values: `system`, `user`, `assistant`, `tool`
`content`	`string` or `array<object>`	Yes	Message content. Can be plain text or an array of content blocks
`name`	string	No	Optional role name
`tool_call_id`	string	No	Used to associate tool calls when `role = tool`

Text example:

{
  "role": "user",
  "content": "Write a product introduction in no more than 50 words."
}

Content block example:

{
  "role": "user",
  "content": [
    {
      "type": "text",
      "text": "Please describe this image."
    },
    {
      "type": "image_url",
      "image_url": {
        "url": "https://cdn.example.com/demo.png"
      }
    }
  ]
}

4. Request Examples

4.1 Standard Non-Streaming Request

curl -X POST "https://direct.reachapi.ai/v1/chat/completions" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "YOUR_MODEL_ID",
    "messages": [
      {
        "role": "user",
        "content": "Introduce ReachAPI in one sentence."
      }
    ],
    "temperature": 0.2
  }'

4.2 Streaming Request

curl -X POST "https://direct.reachapi.ai/v1/chat/completions" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "YOUR_MODEL_ID",
    "messages": [
      {
        "role": "user",
        "content": "Summarize today'\''s priorities in three lines."
      }
    ],
    "stream": true,
    "stream_options": {
      "include_usage": true
    }
  }'

4.3 Request with Tool Definitions

curl -X POST "https://direct.reachapi.ai/v1/chat/completions" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "YOUR_MODEL_ID",
    "messages": [
      {
        "role": "user",
        "content": "Help me check the weather in Shanghai."
      }
    ],
    "tools": [
      {
        "type": "function",
        "function": {
          "name": "get_weather",
          "description": "Get weather information for a city",
          "parameters": {
            "type": "object",
            "properties": {
              "city": {
                "type": "string"
              }
            },
            "required": ["city"]
          }
        }
      }
    ],
    "tool_choice": "auto"
  }'

5. Successful Response

Example non-streaming response:

{
  "id": "chatcmpl_123",
  "object": "chat.completion",
  "created": 1710000000,
  "model": "YOUR_MODEL_ID",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Hello, I am a model-powered assistant."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 12,
    "completion_tokens": 18,
    "total_tokens": 30
  }
}

6. Streaming Response

When stream = true, the endpoint returns OpenAI-style SSE events:

data: {"id":"chatcmpl_123","object":"chat.completion.chunk","choices":[{"index":0,"delta":{"role":"assistant","content":""}}]}

data: {"id":"chatcmpl_123","object":"chat.completion.chunk","choices":[{"index":0,"delta":{"content":"Hello"}}]}

data: [DONE]

7. Error Response

OpenAI-style error example:

{
  "error": {
    "message": "Field `messages` is required",
    "type": "invalid_request_error",
    "param": null,
    "code": "MISSING_REQUIRED_FIELD"
  }
}

Common scenarios:

Missing model in the request body
Missing messages in the request body
Invalid JSON payload
Authentication failure

8. Compatibility Notes

This document lists commonly used fields and example payloads. Actual field names and structures follow the OpenAI Chat Completions API.
This endpoint only covers the Chat Completions path and does not represent the full OpenAI API surface.
If you use newer or experimental official fields, validate them against the actual capabilities available on your gateway.

9. Supported Models and Reference Pricing

The following prices are summarized from the unified pricing document and apply to the GPT text models currently listed. Pricing was checked on 2026-04-17. For detailed pricing rules, refer to gpt.md.

Model	Input	Cached input	Output
`gpt-5.4`	`$2.50 / 1M tokens`	`$0.25 / 1M tokens`	`$15.00 / 1M tokens`
`gpt-5.3-codex`	`$1.75 / 1M tokens`	`$0.175 / 1M tokens`	`$14.00 / 1M tokens`
`gpt-5.2`	`$1.75 / 1M tokens`	`$0.175 / 1M tokens`	`$14.00 / 1M tokens`
`gpt-5.1-codex`	`$1.25 / 1M tokens`	`$0.125 / 1M tokens`	`$10.00 / 1M tokens`
`gpt-5.1`	`$1.25 / 1M tokens`	`$0.125 / 1M tokens`	`$10.00 / 1M tokens`
`gpt-5`	`$1.25 / 1M tokens`	`$0.125 / 1M tokens`	`$10.00 / 1M tokens`
`gpt-5.4-mini`	`$0.75 / 1M tokens`	`$0.075 / 1M tokens`	`$4.50 / 1M tokens`
`gpt-5-mini`	`$0.25 / 1M tokens`	`$0.025 / 1M tokens`	`$2.00 / 1M tokens`

Notes:

Cached input refers to the unit price for cache-hit input tokens
If the model list changes over time, use the dashboard or product configuration as the source of truth for currently enabled models

10. References

OpenAI Chat Completions API: https://platform.openai.com/docs/api-reference/chat/create
OpenAI text generation guide: https://platform.openai.com/docs/guides/text?api-mode=chat
OpenAI API errors: https://platform.openai.com/docs/guides/error-codes/api-errors
Unified platform pricing document: gpt.md

OpenAI Chat API

On this page