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OpenRouter provides a unified API that gives you access to hundreds of AI models through a single endpoint, while automatically handling fallbacks and selecting the most cost-effective options. There are three ways to integrate with OpenRouter, depending on how much control you want:
ApproachBest for
APIFull control, any language, no dependencies
Client SDKsType-safe model calls with minimal overhead
Agent SDKBuilding agents with tool use, loops, and state
Read https://github.com/OpenRouterTeam/skills/tree/main/skills/create-agent-tui and follow the instructions to build an agent using OpenRouter.
Looking for information about free models and rate limits? Please see the FAQ
In the examples below, the OpenRouter-specific headers are optional. Setting them allows your app to appear on the OpenRouter leaderboards. For detailed information about app attribution, see our App Attribution guide.

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Using the OpenRouter API

The most direct way to use OpenRouter. Send standard HTTP requests to the /api/v1/chat/completions endpoint — compatible with any language or framework.
You can use the interactive Request Builder to generate OpenRouter API requests in the language of your choice.
The examples below use ~openai/gpt-latest, a latest alias that always resolves to the newest OpenAI flagship model — so your code keeps using the freshest version without redeploying. You can substitute any model slug here. Browse the full catalog at openrouter.ai/models, or list every available slug programmatically via the GET /api/v1/models endpoint.
import requests
import json

response = requests.post(
  url="https://openrouter.ai/api/v1/chat/completions",
  headers={
    "Authorization": "Bearer <OPENROUTER_API_KEY>",
    "HTTP-Referer": "<YOUR_SITE_URL>", # Optional. Site URL for rankings on openrouter.ai.
    "X-OpenRouter-Title": "<YOUR_SITE_NAME>", # Optional. Site title for rankings on openrouter.ai.
  },
  data=json.dumps({
    "model": "~openai/gpt-latest",
    "messages": [
      {
        "role": "user",
        "content": "What is the meaning of life?"
      }
    ]
  })
)
The API also supports streaming. You can also use the OpenAI SDK pointed at OpenRouter as a drop-in replacement.

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Using the Client SDKs

The Client SDKs wrap the OpenRouter API with full type safety, auto-generated types from the OpenAPI spec, and zero boilerplate. It is intentionally lean — a thin layer over the REST API. First, install the SDK: 
npm install @openrouter/sdk
Then use it in your code: 
import { OpenRouter } from '@openrouter/sdk';

const client = new OpenRouter({
  apiKey: '<OPENROUTER_API_KEY>',
  httpReferer: '<YOUR_SITE_URL>', // Optional. Site URL for rankings on openrouter.ai.
  appTitle: '<YOUR_SITE_NAME>', // Optional. Site title for rankings on openrouter.ai.
});

const completion = await client.chat.send({
  model: '~openai/gpt-latest',
  messages: [
    {
      role: 'user',
      content: 'What is the meaning of life?',
    },
  ],
});

console.log(completion.choices[0].message.content);
See the full Client SDKs documentation for streaming, embeddings, and the complete API reference.

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Using the Agent SDK

The Agent SDK (@openrouter/agent) provides higher-level primitives for building AI agents. It handles multi-turn conversation loops, tool execution, and state management automatically via the callModel function. Install the package: 
npm install @openrouter/agent
Build an agent with tools: 
import { callModel, tool } from '@openrouter/agent';
import { z } from 'zod';

const weatherTool = tool({
  name: 'get_weather',
  description: 'Get the current weather for a location',
  inputSchema: z.object({
    location: z.string().describe('City name'),
  }),
  execute: async ({ location }) => {
    return { temperature: 72, condition: 'sunny', location };
  },
});

const result = await callModel({
  model: '~anthropic/claude-sonnet-latest',
  messages: [
    { role: 'user', content: 'What is the weather in San Francisco?' },
  ],
  tools: [weatherTool],
});

const text = await result.getText();
console.log(text);
The SDK sends the prompt, receives a tool call from the model, executes get_weather, feeds the result back, and returns the final response — all in one callModel invocation. See the full Agent SDK documentation for stop conditions, streaming, dynamic parameters, and more.

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Using the OpenAI SDK

You can also use the OpenAI SDK pointed at OpenRouter as a drop-in replacement. This is useful if you have existing code built on the OpenAI SDK and want to access OpenRouter’s model catalog without changing your code structure. 
import OpenAI from 'openai';

const openai = new OpenAI({
  baseURL: 'https://openrouter.ai/api/v1',
  apiKey: '<OPENROUTER_API_KEY>',
  defaultHeaders: {
    'HTTP-Referer': '<YOUR_SITE_URL>', // Optional. Site URL for rankings on openrouter.ai.
    'X-OpenRouter-Title': '<YOUR_SITE_NAME>', // Optional. Site title for rankings on openrouter.ai.
  },
});

async function main() {
  const completion = await openai.chat.completions.create({
    model: '~openai/gpt-latest',
    messages: [
      {
        role: 'user',
        content: 'What is the meaning of life?',
      },
    ],
  });

  console.log(completion.choices[0].message);
}

main();

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Using third-party SDKs

For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.