Anthropic SDKs

Use this page only when an existing application specifically requires Anthropic Messages. Otherwise, prefer the OpenAI SDK.

The Anthropic SDK base URL is the service origin, without a trailing /v1:

https://omrouter.com

The SDK appends /v1/messages itself.

Python

python -m pip install anthropic

example.py

import os
from anthropic import Anthropic

client = Anthropic(
    api_key=os.environ["OMROUTER_API_KEY"],
    base_url="https://omrouter.com",
)

message = client.messages.create(
    model=os.environ["OMROUTER_MODEL_ID"],
    max_tokens=256,
    messages=[
        {"role": "user", "content": "Reply with one short sentence."}
    ],
)

print(message.content[0].text)

JavaScript

npm install @anthropic-ai/sdk

example.mjs

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

const client = new Anthropic({
  apiKey: process.env.OMROUTER_API_KEY,
  baseURL: 'https://omrouter.com',
});

const message = await client.messages.create({
  model: process.env.OMROUTER_MODEL_ID,
  max_tokens: 256,
  messages: [
    { role: 'user', content: 'Reply with one short sentence.' },
  ],
});

console.log(message.content[0]?.text);

Direct HTTP request

curl --silent --show-error \
  'https://omrouter.com/v1/messages' \
  --header "x-api-key: $OMROUTER_API_KEY" \
  --header 'anthropic-version: 2023-06-01' \
  --header 'content-type: application/json' \
  --data "{
    \"model\": \"$OMROUTER_MODEL_ID\",
    \"max_tokens\": 256,
    \"messages\": [
      {\"role\": \"user\", \"content\": \"Reply with one short sentence.\"}
    ]
  }"

Optional features

Tools, thinking, prompt caching, and image input depend on the selected model. Test the simple message above first, then add these features one at a time.

See Anthropic Messages for all fields.