Kimi K3 API Guide: Integration, Pricing, and Developer Best Practices

The Kimi K3 API provides programmatic access to the 2.8T-parameter model with native vision, 1M-token context, and max-effort reasoning. Pricing starts at $3 per 1M input tokens and $15 per 1M output tokens, with cached input at just $0.30/1M via the Mooncake serving architecture.

### Authentication

export MOONSHOT_API_KEY="sk-your-key-here"
curl https://api.moonshot.ai/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $MOONSHOT_API_KEY" \
  -d '{
    "model": "kimi-k3-thinking",
    "messages": [{"role": "user", "content": "What makes Kimi K3 unique?"}],
    "max_tokens": 1024
  }'

### Node.js Integration

import OpenAI from 'openai';
const client = new OpenAI({
  apiKey: process.env.MOONSHOT_API_KEY,
  baseURL: 'https://api.moonshot.ai/v1',
});
const response = await client.chat.completions.create({
  model: 'kimi-k3-thinking',
  messages: [{ role: 'user', content: 'Analyze this code.' }],
  max_tokens: 4096,
  extra_body: { reasoning_effort: 'max' },
});
console.log(response.choices[0].message.content);

### Key API Features

• **Streaming**: Real-time output via SSE for responsive UIs
• **Vision**: Accept base64 images alongside text in the messages array
• **Context Caching**: Cached inputs at $0.30/1M tokens using prefix matching
• **Reasoning Control**: Adjust reasoning_effort between low, medium, and max

### Best Practices

Enable streaming for better user experience in chat apps. Implement retry logic with exponential backoff for rate limiting. For long conversations, periodically summarize earlier turns to manage token usage efficiently while preserving the 1M-token context capability.