Nous Research Chat API

openapi: 3.1.0
info:
  title: Nous Research Inference API (Nous Portal) Chat API
  version: v1
  description: 'OpenAI-compatible inference API served by Nous Research at https://inference-api.nousresearch.com/v1. Exposes a model catalog and a chat-completions endpoint aggregating Nous Research''s own Hermes models alongside a broad catalog of third-party open and frontier models (OpenRouter-style routing). Requests authenticate with a Nous Portal API key (Bearer token). The API additionally supports the x402 HTTP payment protocol: an un-authenticated request returns HTTP 402 with an `accepts` envelope describing an exact Solana USDC micropayment, enabling pay-per- request agentic access without a pre-provisioned account. This specification was DERIVED by probing the live public API (GET /v1/models returns 200 with the model catalog; POST /v1/chat/completions returns 402 with an x402 payment envelope when unauthenticated). Only endpoints observed on the live host are described here; other OpenAI- compatible routes may exist but were not verified.'
  x-source: https://inference-api.nousresearch.com/v1
  x-derived-by: api-evangelist enrichment pipeline (live probe)
servers:
- url: https://inference-api.nousresearch.com/v1
  description: Nous Research inference API (production)
security:
- bearerAuth: []
tags:
- name: Chat
  description: OpenAI-compatible chat completions.
paths:
  /chat/completions:
    post:
      tags:
      - Chat
      operationId: createChatCompletion
      summary: Create a chat completion
      description: 'OpenAI-compatible chat completions. Provide a `model` id from GET /models and a `messages` array. Supports streaming via Server-Sent Events when `stream: true`. Authenticate with a Nous Portal API key as `Authorization: Bearer <key>`; alternatively an un-authenticated request returns HTTP 402 with an x402 Solana USDC payment envelope for pay-per-request access.'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ChatCompletionRequest'
      responses:
        '200':
          description: The chat completion result (or an SSE stream when `stream` is true).
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ChatCompletion'
        '400':
          description: Malformed request.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '401':
          description: Missing or invalid API key.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '402':
          description: Payment required. Returned for un-authenticated requests; body is an x402 payment envelope describing the exact Solana USDC micropayment accepted for this request.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/X402PaymentRequired'
        '429':
          description: Rate limited.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
components:
  schemas:
    X402PaymentRequired:
      type: object
      description: x402 payment envelope returned with HTTP 402.
      properties:
        x402Version:
          type: integer
          example: 1
        accepts:
          type: array
          items:
            type: object
            properties:
              scheme:
                type: string
                example: exact
              network:
                type: string
                example: solana
              maxAmountRequired:
                type: string
              resource:
                type: string
              description:
                type: string
              mimeType:
                type: string
              payTo:
                type: string
              maxTimeoutSeconds:
                type: integer
              asset:
                type: string
                description: Token mint (USDC on Solana).
        error:
          type: string
    Error:
      type: object
      properties:
        error:
          type: object
          properties:
            message:
              type: string
            type:
              type: string
            code:
              type: string
    ChatCompletionRequest:
      type: object
      properties:
        model:
          type: string
          description: A model id from GET /models.
          example: nousresearch/hermes-4-405b
        messages:
          type: array
          items:
            $ref: '#/components/schemas/ChatMessage'
        stream:
          type: boolean
          description: Stream the response as Server-Sent Events.
          default: false
        temperature:
          type: number
        max_tokens:
          type: integer
        top_p:
          type: number
        tools:
          type: array
          items:
            type: object
      required:
      - model
      - messages
    ChatCompletion:
      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:
          type: object
          properties:
            prompt_tokens:
              type: integer
            completion_tokens:
              type: integer
            total_tokens:
              type: integer
    ChatMessage:
      type: object
      properties:
        role:
          type: string
          enum:
          - system
          - user
          - assistant
          - tool
        content:
          type: string
      required:
      - role
      - content
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: 'Nous Portal API key supplied as: Authorization: Bearer <key>'