Nscale Serverless Chat Completions API

openapi: 3.0.1
info:
  title: Nscale Serverless Inference API
  description: >-
    OpenAI-compatible serverless inference API for Nscale. Provides chat
    completions, text completions, embeddings, image generation, and model
    discovery against open models (Llama, Qwen, DeepSeek, GPT OSS, Mistral,
    Flux) served on Nscale GPU infrastructure. Authenticate with a Bearer API
    key issued from the Nscale console.
  termsOfService: https://www.nscale.com/legal/terms-of-service
  contact:
    name: Nscale Support
    url: https://docs.nscale.com
  version: '1.0'
servers:
  - url: https://inference.api.nscale.com/v1
    description: Serverless Inference API
security:
  - bearerAuth: []
tags:
  - name: Chat
    description: OpenAI-compatible chat completions.
  - name: Completions
    description: OpenAI-compatible legacy text completions.
  - name: Embeddings
    description: Vector embeddings of text input.
  - name: Images
    description: Text-to-image generation.
  - name: Models
    description: Model catalog discovery.
paths:
  /chat/completions:
    post:
      operationId: createChatCompletion
      tags:
        - Chat
      summary: Create a chat completion
      description: >-
        Generates a chat completion response for the provided model and chat
        history. Supports streaming via Server-Sent Events when stream is true.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ChatCompletionRequest'
      responses:
        '200':
          description: A chat completion (or an SSE stream when stream=true).
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ChatCompletionResponse'
            text/event-stream:
              schema:
                type: string
                description: Server-Sent Events stream of ChatCompletionChunk objects.
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/RateLimited'
  /completions:
    post:
      operationId: createCompletion
      tags:
        - Completions
      summary: Create a completion
      description: Generates a completion response for the provided model and prompt.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CompletionRequest'
      responses:
        '200':
          description: A text completion.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CompletionResponse'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/RateLimited'
  /embeddings:
    post:
      operationId: createEmbedding
      tags:
        - Embeddings
      summary: Create embeddings
      description: >-
        Returns a vector representation of a given input that can be consumed by
        machine learning models and retrieval systems.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/EmbeddingRequest'
      responses:
        '200':
          description: A list of embedding vectors.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/EmbeddingResponse'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/RateLimited'
  /images/generations:
    post:
      operationId: createImage
      tags:
        - Images
      summary: Create an image
      description: Creates one or more images based on the provided text prompt.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ImageGenerationRequest'
      responses:
        '200':
          description: The generated image(s).
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ImageGenerationResponse'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/RateLimited'
  /models:
    get:
      operationId: listModels
      tags:
        - Models
      summary: List models
      description: >-
        Returns a list of serverless models available for inference, including
        identifiers and metadata such as context length and pricing.
      responses:
        '200':
          description: A list of available models.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ModelList'
        '401':
          $ref: '#/components/responses/Unauthorized'
  /models/{model}:
    get:
      operationId: retrieveModel
      tags:
        - Models
      summary: Retrieve a model
      description: Returns metadata for a single model by identifier.
      parameters:
        - name: model
          in: path
          required: true
          description: The model identifier.
          schema:
            type: string
      responses:
        '200':
          description: The requested model.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Model'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          description: Model not found.
components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: >-
        Nscale API key issued from the console, sent as
        `Authorization: Bearer $NSCALE_API_KEY`.
  responses:
    Unauthorized:
      description: Missing or invalid API key.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    RateLimited:
      description: Too many requests; back off and retry.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  schemas:
    ChatCompletionRequest:
      type: object
      required:
        - model
        - messages
      properties:
        model:
          type: string
          description: Model identifier, e.g. meta-llama/Llama-4-Scout-17B-16E-Instruct.
        messages:
          type: array
          items:
            $ref: '#/components/schemas/ChatMessage'
        temperature:
          type: number
          format: float
          minimum: 0
          maximum: 2
          default: 1
        top_p:
          type: number
          format: float
          minimum: 0
          maximum: 1
          default: 1
        max_tokens:
          type: integer
          description: Maximum number of tokens to generate.
        stream:
          type: boolean
          default: false
          description: If true, partial deltas are sent as Server-Sent Events.
        stop:
          oneOf:
            - type: string
            - type: array
              items:
                type: string
        frequency_penalty:
          type: number
          format: float
          minimum: -2
          maximum: 2
          default: 0
        presence_penalty:
          type: number
          format: float
          minimum: -2
          maximum: 2
          default: 0
        tools:
          type: array
          items:
            type: object
        tool_choice:
          oneOf:
            - type: string
            - type: object
    ChatMessage:
      type: object
      required:
        - role
        - content
      properties:
        role:
          type: string
          enum:
            - system
            - user
            - assistant
            - tool
        content:
          description: Text content or an array of multimodal content parts.
          oneOf:
            - type: string
            - type: array
              items:
                type: object
        name:
          type: string
    ChatCompletionResponse:
      type: object
      properties:
        id:
          type: string
        object:
          type: string
          example: chat.completion
        created:
          type: integer
        model:
          type: string
        choices:
          type: array
          items:
            type: object
            properties:
              index:
                type: integer
              message:
                $ref: '#/components/schemas/ChatMessage'
              finish_reason:
                type: string
        usage:
          $ref: '#/components/schemas/Usage'
    CompletionRequest:
      type: object
      required:
        - model
        - prompt
      properties:
        model:
          type: string
        prompt:
          oneOf:
            - type: string
            - type: array
              items:
                type: string
        max_tokens:
          type: integer
        temperature:
          type: number
          format: float
        top_p:
          type: number
          format: float
        stream:
          type: boolean
          default: false
        stop:
          oneOf:
            - type: string
            - type: array
              items:
                type: string
    CompletionResponse:
      type: object
      properties:
        id:
          type: string
        object:
          type: string
          example: text_completion
        created:
          type: integer
        model:
          type: string
        choices:
          type: array
          items:
            type: object
            properties:
              index:
                type: integer
              text:
                type: string
              finish_reason:
                type: string
        usage:
          $ref: '#/components/schemas/Usage'
    EmbeddingRequest:
      type: object
      required:
        - model
        - input
      properties:
        model:
          type: string
          description: Embedding model identifier, e.g. Qwen/Qwen3-Embedding-8B.
        input:
          description: Text or array of text to embed.
          oneOf:
            - type: string
            - type: array
              items:
                type: string
        encoding_format:
          type: string
          enum:
            - float
            - base64
          default: float
    EmbeddingResponse:
      type: object
      properties:
        object:
          type: string
          example: list
        data:
          type: array
          items:
            type: object
            properties:
              object:
                type: string
                example: embedding
              index:
                type: integer
              embedding:
                type: array
                items:
                  type: number
                  format: float
        model:
          type: string
        usage:
          $ref: '#/components/schemas/Usage'
    ImageGenerationRequest:
      type: object
      required:
        - model
        - prompt
      properties:
        model:
          type: string
          description: Image model identifier, e.g. BlackForestLabs/FLUX.1-schnell.
        prompt:
          type: string
        n:
          type: integer
          default: 1
          description: Number of images to generate.
        size:
          type: string
          description: Output dimensions, e.g. 1024x1024.
        response_format:
          type: string
          enum:
            - url
            - b64_json
          default: b64_json
        num_inference_steps:
          type: integer
          description: Number of diffusion steps (affects per-megapixel cost).
    ImageGenerationResponse:
      type: object
      properties:
        created:
          type: integer
        data:
          type: array
          items:
            type: object
            properties:
              url:
                type: string
              b64_json:
                type: string
    ModelList:
      type: object
      properties:
        object:
          type: string
          example: list
        data:
          type: array
          items:
            $ref: '#/components/schemas/Model'
    Model:
      type: object
      properties:
        id:
          type: string
        object:
          type: string
          example: model
        created:
          type: integer
        owned_by:
          type: string
        context_length:
          type: integer
        pricing:
          type: object
          description: Per-1M-token pricing metadata where exposed.
          additionalProperties: true
    Usage:
      type: object
      properties:
        prompt_tokens:
          type: integer
        completion_tokens:
          type: integer
        total_tokens:
          type: integer
    Error:
      type: object
      properties:
        error:
          type: object
          properties:
            message:
              type: string
            type:
              type: string
            code:
              type: string