The European AI gateway
for agents

# Add the Opper AI gateway

Set up Opper so this project can call 700+ AI models through a single API.

## Step 1: Get an API key

Have the user sign up at https://opper.ai/sign-up/free and create an API key. Set it as `OPPER_API_KEY` in the environment.

## Step 2: Use the OpenAI SDK with Opper's compat endpoint

```ts
import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.OPPER_API_KEY,
  baseURL: "https://api.opper.ai/v3/compat",
});

const completion = await client.chat.completions.create({
  model: "anthropic/claude-sonnet-4-5",
  messages: [{ role: "user", content: "Hello" }],
});
```

## When to use what

- **Drop-in OpenAI SDK swap (above)** — fastest path, works with any existing OpenAI SDK code.
- **Agent SDK (Python or TypeScript)** — building autonomous agents with tools, MCP, span tracing, multi-agent composition. https://docs.opper.ai/agents
- **Structured outputs** — typed input/output with schemas. https://docs.opper.ai/build/task/calls
- **Indexes** — semantic storage for RAG. https://docs.opper.ai/capabilities/indexes
- **Agent CLI** — launch existing agents (Claude Code, Codex, OpenCode, ...) on Opper's gateway. https://opper.ai/agent-cli

## Critical rules

- Read `OPPER_API_KEY` from env, never hardcode
- Pass models as `provider/model` strings (e.g. `anthropic/claude-opus-4-7`, `openai/gpt-5`)
- Use baseURL `https://api.opper.ai/v3/compat`
- No markup on tokens. A 3% fee applies on credit purchases
- 700+ models available — see https://docs.opper.ai/capabilities/models

Full docs (agent-readable): https://opper.ai/llms-full.txt