LiteLLM

LiteLLM Messages API

The Messages API from LiteLLM — 2 operation(s) for messages.

GitHub OpenAPI

Documentation

📖
Documentation
https://docs.litellm.ai/docs/completion
📖
GettingStarted
https://docs.litellm.ai/docs/proxy/quick_start

Specifications

⚙
OpenAPI
https://raw.githubusercontent.com/api-evangelist/litellm/refs/heads/main/openapi/litellm-messages-api-openapi.yml

OpenAPI Specification

litellm-messages-api-openapi.yml Raw ↑ 
openapi: 3.1.0
info:
  title: LiteLLM Proxy Assistants Messages API
  description: Minimal OpenAPI 3.1 specification for the LiteLLM proxy server, covering chat completions, completions, embeddings, audio, images, moderations, fine-tuning, batches, assistants, vector stores, messages, OCR, rerank, and RAG endpoints.
  version: 1.0.0
servers:
- url: http://localhost:4000
  description: LiteLLM proxy server
tags:
- name: Messages
paths:
  /v1/messages:
    post:
      operationId: createMessage
      summary: Create a message (Anthropic-compatible)
      responses:
        '200':
          description: Message result
        default:
          description: Error response
      tags:
      - Messages
  /v1/messages/count_tokens:
    post:
      operationId: countMessageTokens
      summary: Count tokens for a message
      responses:
        '200':
          description: Token count
        default:
          description: Error response
      tags:
      - Messages
x-generated-from: https://docs.litellm.ai/docs/completion
x-generated-by: claude-crawl-2026-05-08