LongCat API Platform Quick Start Guide ​

Welcome to the LongCat API Platform! This document will help you get started quickly and begin using our large model services.

How to Get an API Key? ​

Register an Account ​

1. Visit LongCat API Platform
2. Fill in the required information to complete account registration

Create Your API Key ​

1. After registering and logging in, go to the API Keys page and click “Create API Key” to manually generate a key.
2. Once created, you can view the following details in the list:
   • Name: Your custom identifier for the application
   • Key: The system-generated secret (Your API key is only shown once upon creation. Please copy and store it securely — if lost, you'll need to create a new one.)

Supported API Types ​

LongCat API Platform is compatible with two mainstream API formats. You can choose according to your needs:

OpenAI API Format ​

Fully compatible with the OpenAI API specification, supporting the following endpoints:

• Chat Completion: /v1/chat/completions

Anthropic API Format ​

Compatible with the Anthropic Claude API specification, supporting the following endpoint:

• Message Chat: /v1/messages

Endpoints ​

• OpenAI Format: https://api.longcat.chat/openai
• Anthropic Format: https://api.longcat.chat/anthropic

Supported Models ​

Rate Limiting Rules ​

Single Request Limit ​

• Maximum context length:
  • LongCat-2.0: 1M token context window with a maximum output length of 128K tokens

Over-limit Handling ​

When rate limiting is triggered, the API will return HTTP status code 429. Example response:

{
  "error": {
    "code": "rate_limit_exceeded",
    "message": "Request rate limit exceeded, please try again later",
    "type": "rate_limit_error",
    "retry_after": 60
  }
}

It is recommended to implement exponential backoff retry mechanism on the client side.

Quick Integration Examples ​

OpenAI API Format Example ​

Python Example ​

import requests

url = "https://api.longcat.chat/openai/v1/chat/completions"
headers = {
    "Authorization": "Bearer YOUR_APP_KEY",
    "Content-Type": "application/json"
}

data = {
    "model": "LongCat-2.0",
    "messages": [
        {"role": "user", "content": "Hello, please introduce yourself."}
    ],
    "max_tokens": 1000,
    "temperature": 0.7
}

response = requests.post(url, headers=headers, json=data)
print(response.json())

Using OpenAI SDK ​

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_APP_KEY",
    base_url="https://api.longcat.chat/openai"
)

response = client.chat.completions.create(
    model="LongCat-2.0",
    messages=[
        {"role": "user", "content": "Hello!"}
    ],
    max_tokens=1000
)

print(response.choices[0].message.content)

Anthropic API Format Example ​

Using Anthropic SDK ​

from anthropic import Anthropic

client = Anthropic(
    api_key="Authorization: Bearer YOUR_APP_KEY",
    base_url="https://api.longcat.chat/anthropic/",
    default_headers={
        "Content-Type": "application/json",
        "Authorization": "Bearer YOUR_APP_KEY",
    }
)


response = client.messages.create(
    model="LongCat-2.0",
    max_tokens=1000,
    messages=[
        {"role": "user", "content": "Hello!"}
    ]
)

print(response.content[0].text)

cURL Example ​

OpenAI Format ​

curl -X POST https://api.longcat.chat/openai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_APP_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "LongCat-2.0",
    "messages": [{"role": "user", "content": "Hello!"}],
    "max_tokens": 1000
  }'

Anthropic Format ​

curl -X POST https://api.longcat.chat/anthropic/v1/messages \
  -H "Authorization: Bearer YOUR_APP_KEY" \
  -H "Content-Type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "LongCat-2.0",
    "max_tokens": 1000,
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

Important Reminders ​

• Please keep your API Key safe to avoid quota theft due to leakage

Now you have learned the basics of using the LongCat API Platform. Go ahead and try it out!