openrouter-hello-world

OpenRouter Hello World

Overview

Send a minimal chat completion request through OpenRouter, understand the response format, try different models, and verify the full round-trip works. All requests go to the single endpoint POST https://openrouter.ai/api/v1/chat/completions.

Minimal Request (cURL)

curl -s https://openrouter.ai/api/v1/chat/completions \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "google/gemma-2-9b-it:free",
    "messages": [{"role": "user", "content": "Say hello in three languages"}],
    "max_tokens": 100
  }' | jq .

Response Format

{
  "id": "gen-abc123xyz",
  "model": "google/gemma-2-9b-it:free",
  "object": "chat.completion",
  "created": 1711234567,
  "choices": [{
    "index": 0,
    "message": {
      "role": "assistant",
      "content": "Hello! Bonjour! Hola!"
    },
    "finish_reason": "stop"
  }],
  "usage": {
    "prompt_tokens": 12,
    "completion_tokens": 8,
    "total_tokens": 20
  }
}

Key fields:

• id (gen-...) -- use this to query generation stats via GET /api/v1/generation?id=gen-abc123xyz
• model -- confirms which model actually served the request
• usage -- token counts for cost calculation
• finish_reason -- stop (complete), length (hit max_tokens), tool_calls (function call)

Python Example

from openai import OpenAI
import os

client = OpenAI(
    base_url="https://openrouter.ai/api/v1",
    api_key=os.environ["OPENROUTER_API_KEY"],
    default_headers={"HTTP-Referer": "https://your-app.com", "X-Title": "My App"},
)

# Basic completion
response = client.chat.completions.create(
    model="google/gemma-2-9b-it:free",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "What is OpenRouter in one sentence?"},
    ],
    max_tokens=100,
)

print(response.choices[0].message.content)
print(f"Model: {response.model}")
print(f"Tokens: {response.usage.prompt_tokens} prompt + {response.usage.completion_tokens} completion")

TypeScript Example

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://openrouter.ai/api/v1",
  apiKey: process.env.OPENROUTER_API_KEY,
  defaultHeaders: { "HTTP-Referer": "https://your-app.com", "X-Title": "My App" },
});

const res = await client.chat.completions.create({
  model: "google/gemma-2-9b-it:free",
  messages: [{ role: "user", content: "What is OpenRouter in one sentence?" }],
  max_tokens: 100,
});

console.log(res.choices[0].message.content);
console.log(`Model: ${res.model} | Tokens: ${res.usage?.total_tokens}`);

Try Different Models

# Swap model ID to access any of 400+ models
models_to_try = [
    "google/gemma-2-9b-it:free",         # Free tier
    "meta-llama/llama-3.1-8b-instruct",  # Open-source
    "anthropic/claude-3.5-sonnet",        # Anthropic
    "openai/gpt-4o",                      # OpenAI
    "openrouter/auto",                    # Auto-router (picks best model)
]

for model_id in models_to_try:
    try:
        r = client.chat.completions.create(
            model=model_id,
            messages=[{"role": "user", "content": "Hi"}],
            max_tokens=10,
        )
        print(f"{model_id}: {r.choices[0].message.content}")
    except Exception as e:
        print(f"{model_id}: {e}")

Check Generation Cost

# After a request, query the generation endpoint for cost details
curl -s "https://openrouter.ai/api/v1/generation?id=gen-abc123xyz" \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" | jq '{
    model: .data.model,
    tokens_prompt: .data.tokens_prompt,
    tokens_completion: .data.tokens_completion,
    total_cost: .data.total_cost
  }'

Error Handling

HTTP	Cause	Fix
401	Invalid or missing API key	Verify sk-or-v1-... key is exported
402	Insufficient credits for paid model	Add credits or use a :free model
404	Wrong base URL or invalid model ID	Use https://openrouter.ai/api/v1; check model ID at /api/v1/models
400	Malformed JSON or missing messages	Ensure messages array has objects with role and content

Enterprise Considerations

• Always set max_tokens to prevent unbounded completions
• Use HTTP-Referer and X-Title headers for usage attribution in dashboards
• Query /api/v1/generation?id= for async cost auditing
• Test with free models first, then switch to paid models for production

References

• Examples | Errors
• OpenRouter Quickstart | API Reference