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

Model NameAPI FormatDescription
LongCat-2.0-PreviewOpenAI/AnthropicHigh-performance Agentic model

How to Get Usage Quota?

Daily Free Quota

  • LongCat-2.0-Preview offers an initial quota of 5,000,000 Tokens/day. You can submit model feedback; each valid submission has a chance to earn a quota refresh, up to a daily maximum of 120,000,000 Tokens
  • The free quota is refreshed automatically at midnight (Beijing Time) every day
  • Unused quota from the previous day will be cleared and will not roll over to the next day

Quota Usage Instructions

  • Both input and output Tokens are counted towards consumption
  • Streaming and non-streaming endpoints consume quota equally

Quota Inquiry

You can view your usage in real time at Usage

Note: The platform is currently in public beta and does not support paid quota purchases.

Rate Limiting Rules

Single Request Limit

  • Maximum context length:
    • LongCat-2.0-Preview: 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-Preview",
    "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-Preview",
    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-Preview",
    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-Preview",
    "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-Preview",
    "max_tokens": 1000,
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

Important Reminders

  • Please use your daily free quota reasonably. Unused quota will not be retained for the next day
  • 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!

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