> ## Documentation Index > Fetch the complete documentation index at: https://evolink.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # GPT All-Model API - Chat Completions Quickstart > - Call GPT series text models using the OpenAI SDK format (select the specific model via the `model` parameter) - Reasoning + tool-calling models, supporting mixed text and image input - Synchronous processing mode, minimal parameters, quick to get started - 💡 Need more parameters? See the [full parameter reference](./chat-completions-reference) - 💡 Need server-side tools (web search, code execution)? Use the [Responses API](../responses/responses-quickstart) **BaseURL**: The default BaseURL is `https://direct.evolink.ai`, which has better support for text models and long-lived connections. `https://api.evolink.ai` is the primary endpoint for multimodal services and serves as a fallback address for text models. ## OpenAPI ````yaml en/api-manual/language-series/gpt/chat-completions/chat-completions-quickstart.json POST /v1/chat/completions openapi: 3.1.0 info: title: GPT All-Model API - Chat Completions Quickstart description: >- Quickstart examples for calling GPT series text models through the OpenAI-compatible Chat Completions API. license: name: MIT version: 1.0.0 servers: - url: https://direct.evolink.ai description: Production (recommended) - url: https://api.evolink.ai description: Alternative URL security: - bearerAuth: [] tags: - name: Chat Completions description: OpenAI-compatible chat completions API paths: /v1/chat/completions: post: tags: - Chat Completions summary: GPT Quick Chat (All Models) description: >- - Call GPT series text models using the OpenAI SDK format (select the specific model via the `model` parameter) - Reasoning + tool-calling models, supporting mixed text and image input - Synchronous processing mode, minimal parameters, quick to get started - 💡 Need more parameters? See the [full parameter reference](./chat-completions-reference) - 💡 Need server-side tools (web search, code execution)? Use the [Responses API](../responses/responses-quickstart) operationId: gptChatCompletionsQuickstart requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/ChatCompletionQuickRequest' responses: '200': description: Chat completion successful content: application/json: schema: $ref: '#/components/schemas/ChatCompletionResponse' '400': description: Invalid request parameters content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: 400 message: Invalid request parameters type: invalid_request_error '401': description: Unauthorized, invalid or expired token content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: 401 message: Invalid or expired token type: authentication_error '402': description: Insufficient quota content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: 402 message: Insufficient quota type: insufficient_quota_error fallback_suggestion: https://evolink.ai/dashboard/billing '429': description: Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: 429 message: Rate limit exceeded type: rate_limit_error fallback_suggestion: retry after 60 seconds '500': description: Internal server error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: 500 message: Internal server error type: internal_server_error fallback_suggestion: try again later '503': description: Service temporarily unavailable content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: 503 message: Service temporarily unavailable type: service_unavailable_error fallback_suggestion: retry after 30 seconds components: schemas: ChatCompletionQuickRequest: type: object required: - model - messages properties: model: type: string description: >- Model to call: | Model ID | Context window | Positioning | |---|---|---| | `gpt-5.6-sol` | 1,050,000 | GPT-5.6 family, frontier reasoning | | `gpt-5.6-terra` | 1,050,000 | GPT-5.6 family, balanced production | | `gpt-5.6-luna` | 1,050,000 | GPT-5.6 family, high throughput and cost control | | `gpt-5.5` | 400,000 | General-purpose reasoning model | | `gpt-5.4` | 128,000 | General-purpose reasoning model | | `gpt-5.2` | 400,000 | General-purpose reasoning model | | `gpt-5.1` | 400,000 | General-purpose reasoning model | enum: - gpt-5.6-sol - gpt-5.6-terra - gpt-5.6-luna - gpt-5.5 - gpt-5.4 - gpt-5.2 - gpt-5.1 example: gpt-5.6-sol messages: type: array description: >- List of chat messages. For multimodal usage such as images, see the [full parameter reference](./chat-completions-reference). ```json "messages": [ { "role": "user", "content": [ { "type": "text", "text": "What is in this image?" }, { "type": "image_url", "image_url": { "url": "https://example.com/photo.png" } } ] } ] ``` items: $ref: '#/components/schemas/MessageSimple' example: - role: user content: Explain quantum entanglement in one sentence. ChatCompletionResponse: type: object properties: id: type: string description: Unique identifier for this conversation example: chatcmpl-CvJ2p8mQxK7nR4wS object: type: string enum: - chat.completion description: Response type example: chat.completion created: type: integer description: Creation timestamp example: 1786705221 model: type: string description: Actual model name used example: gpt-5.6-sol choices: type: array description: List of generated results items: $ref: '#/components/schemas/Choice' usage: $ref: '#/components/schemas/Usage' ErrorResponse: type: object properties: error: type: object properties: code: type: integer description: HTTP status error code message: type: string description: Error description type: type: string description: Error type param: type: string description: Related parameter name fallback_suggestion: type: string description: Suggestion when error occurs MessageSimple: type: object required: - role - content properties: role: type: string description: Message role enum: - system - developer - user - assistant example: user content: description: >- Message content: a string, or an array of content blocks (`text` / `image_url`). example: Explain quantum entanglement in one sentence. oneOf: - type: string - type: array items: type: object Choice: type: object properties: index: type: integer description: Result index example: 0 message: $ref: '#/components/schemas/AssistantMessage' finish_reason: type: string description: >- Finish reason: `stop` for a normal ending, `length` when the maximum token limit is reached, `tool_calls` when a tool call is required example: stop Usage: type: object description: >- Token usage statistics. Prompt caching applies automatically, and cached input tokens are billed at the lower cached rate. properties: prompt_tokens: type: integer description: Number of input tokens example: 18 completion_tokens: type: integer description: Number of output tokens (includes reasoning tokens) example: 42 total_tokens: type: integer description: Total number of tokens example: 60 prompt_tokens_details: type: object description: Detailed input token information properties: cached_tokens: type: integer description: Number of tokens served from cache example: 0 AssistantMessage: type: object properties: role: type: string enum: - assistant example: assistant content: type: string description: Text content generated by the model example: >- Quantum entanglement means the states of two particles are correlated, so measuring one instantly determines the state of the other. securitySchemes: bearerAuth: type: http scheme: bearer description: >- ##All APIs require Bearer Token authentication## **Get API Key:** Visit [API Key Management Page](https://evolink.ai/dashboard/keys) to get your API Key **Add to request header:** ``` Authorization: Bearer YOUR_API_KEY ``` ````