Featherless AI Completions API

openapi: 3.0.1
info:
  title: Featherless AI Chat Completions API
  description: OpenAI-compatible REST API for the Featherless AI serverless inference platform. A single Bearer-authenticated interface serves thousands of open-weight Hugging Face models for chat completions, legacy text completions, embeddings, and model discovery. Pricing is a flat monthly subscription with unlimited tokens rather than per-token billing.
  termsOfService: https://featherless.ai/terms
  contact:
    name: Featherless AI Support
    url: https://featherless.ai
  version: '1.0'
servers:
- url: https://api.featherless.ai/v1
  description: OpenAI-compatible base URL for Featherless AI inference.
security:
- bearerAuth: []
tags:
- name: Completions
  description: OpenAI-compatible legacy text completions.
paths:
  /completions:
    post:
      operationId: createCompletion
      tags:
      - Completions
      summary: Create a text completion
      description: 'Generates a text completion for the provided prompt. OpenAI compatible. The `prompt` may be a string or an array of strings; an array is treated as a parallel inference call. Supports streaming via `stream: true`.'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateCompletionRequest'
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CreateCompletionResponse'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '429':
          $ref: '#/components/responses/TooManyRequests'
components:
  responses:
    Unauthorized:
      description: Missing or invalid API key.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    TooManyRequests:
      description: Concurrency limit for the account's plan exceeded. Featherless meters concurrent connections rather than tokens.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  schemas:
    Usage:
      type: object
      properties:
        prompt_tokens:
          type: integer
        completion_tokens:
          type: integer
        total_tokens:
          type: integer
    CreateCompletionRequest:
      type: object
      required:
      - model
      - prompt
      properties:
        model:
          type: string
          description: Hugging Face model identifier.
        prompt:
          description: Prompt to complete. A string, or an array of strings treated as a parallel inference call.
          oneOf:
          - type: string
          - type: array
            items:
              type: string
        temperature:
          type: number
          nullable: true
        top_p:
          type: number
          nullable: true
        top_k:
          type: integer
          nullable: true
        min_p:
          type: number
          nullable: true
        repetition_penalty:
          type: number
          nullable: true
        max_tokens:
          type: integer
          nullable: true
        stop:
          oneOf:
          - type: string
          - type: array
            items:
              type: string
          nullable: true
        stream:
          type: boolean
          default: false
    Error:
      type: object
      properties:
        error:
          type: object
          properties:
            message:
              type: string
            type:
              type: string
            code:
              type: string
              nullable: true
    CreateCompletionResponse:
      type: object
      properties:
        id:
          type: string
        object:
          type: string
          enum:
          - 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
                nullable: true
        usage:
          $ref: '#/components/schemas/Usage'
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: Featherless API key
      description: 'Set `Authorization: Bearer <FEATHERLESS_API_KEY>`. Keys are created in the Featherless dashboard.'