Anthropic SDK

The gateway accepts Anthropic-shaped requests on a separate path so the official anthropic SDK works without a custom adapter. Use this when your codebase is already standardised on Anthropic’s messages.create() style.

Python

pip install anthropic

import os
from anthropic import Anthropic

client = Anthropic(
    base_url="https://lowrouter.ai/api/v1/anthropic",
    api_key=os.environ["LOWROUTER_API_KEY"],
)

message = client.messages.create(
    model="anthropic/claude-sonnet-4-5",
    max_tokens=512,
    messages=[
        {"role": "user", "content": "In one sentence, what is a vector database?"}
    ],
)

print(message.content[0].text)

TypeScript

npm install @anthropic-ai/sdk

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  baseURL: "https://lowrouter.ai/api/v1/anthropic",
  apiKey: process.env.LOWROUTER_API_KEY,
});

const message = await client.messages.create({
  model: "anthropic/claude-sonnet-4-5",
  max_tokens: 512,
  messages: [{ role: "user", content: "What's a vector database?" }],
});

console.log(message.content);

Notes

• The model string is the LowRouter ID (anthropic/claude-sonnet-4-5), not Anthropic’s bare model name.
• api_key is your LowRouter key, not an Anthropic API key.
• The anthropic-version header is set automatically by the SDK; the gateway accepts what the SDK sends.
• Streaming works as in the official SDK (client.messages.stream(...)).
• Eco metadata is appended to the response in a lowrouter field at the top level, the same shape as in the OpenAI-compatible path.

When to prefer this over the OpenAI path

• Your codebase already uses Anthropic types end-to-end and you don’t want to rewrite call-sites.
• You depend on Anthropic-specific request features (system prompt caching, citations, computer-use tool blocks) that aren’t in the OpenAI schema.
• You want to keep tool definitions in Anthropic’s tools shape.

If neither of these applies, the OpenAI-compatible path is simpler: one set of types, one base URL, every model on the same endpoint.