Onlist

SDKs

Onlist provides official SDKs for Python and JavaScript/TypeScript. They wrap the OpenAI client, so every chat.completions, embeddings, and images call works out of the box with zero configuration: the base URL and auth header are handled for you.

You do not need an SDK to use Onlist. Any OpenAI-compatible client works with a base URL swap (see Quickstart and Tool Configuration). The SDKs add convenience: auto-configured endpoints, ONLIST_API_KEY env var support, and a typed marketplace namespace for browsing models and providers.

Python

Install

pip install onlist

Usage

from onlist import Onlist

client = Onlist()  # reads ONLIST_API_KEY env var

response = client.chat.completions.create(
    model="anthropic/claude-sonnet-4",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)

Authentication

The client looks for a key in this order:

  1. api_key constructor parameter
  2. ONLIST_API_KEY environment variable
  3. OPENAI_API_KEY environment variable (fallback for easy migration)
# Explicit key
client = Onlist(api_key="sk-...")

# Or set the env var
# export ONLIST_API_KEY=sk-...
client = Onlist()

Provider routing

Use extra_body to pass the provider object:

response = client.chat.completions.create(
    model="openai/gpt-4o",
    messages=[{"role": "user", "content": "Hello"}],
    extra_body={"provider": {"sort": "price"}},
)

Streaming

stream = client.chat.completions.create(
    model="anthropic/claude-sonnet-4",
    messages=[{"role": "user", "content": "Tell me a story"}],
    stream=True,
)

for chunk in stream:
    content = chunk.choices[0].delta.content
    if content:
        print(content, end="", flush=True)

JavaScript / TypeScript

Install

npm install @onlist/sdk

Usage

import { Onlist } from "@onlist/sdk";

const client = new Onlist();  // reads ONLIST_API_KEY env var

const response = await client.chat.completions.create({
  model: "anthropic/claude-sonnet-4",
  messages: [{ role: "user", content: "Hello!" }],
});
console.log(response.choices[0].message.content);

Authentication

The client looks for a key in this order:

  1. apiKey constructor parameter
  2. ONLIST_API_KEY environment variable
  3. OPENAI_API_KEY environment variable (fallback for easy migration)
// Explicit key
const client = new Onlist({ apiKey: "sk-..." });

// Or set the env var
// export ONLIST_API_KEY=sk-...
const client = new Onlist();

Provider routing

Pass the provider field directly:

const response = await client.chat.completions.create({
  model: "openai/gpt-4o",
  messages: [{ role: "user", content: "Hello" }],
  provider: { sort: "price" },
});

Streaming

const stream = await client.chat.completions.create({
  model: "anthropic/claude-sonnet-4",
  messages: [{ role: "user", content: "Tell me a story" }],
  stream: true,
});

for await (const chunk of stream) {
  const content = chunk.choices[0]?.delta?.content;
  if (content) process.stdout.write(content);
}

Marketplace API

Both SDKs expose a marketplace namespace for browsing the Onlist catalog programmatically.

# List models with pricing
models = client.marketplace.models.list(limit=10)
for m in models.data:
    print(f"{m.id}: ${m.pricing.prompt}/M input tokens")

# Get a specific model with all provider offers
detail = client.marketplace.models.get("anthropic/claude-sonnet-4")
for offer in detail.providers:
    print(f"{offer.name}: ${offer.price_input_usd}/M input")

# List providers
providers = client.marketplace.providers.list()
for p in providers.items:
    print(f"{p.name} ({p.listing_count} models)")

Migration from OpenAI

Replace the import and constructor. All existing method calls stay the same.

- from openai import OpenAI
+ from onlist import Onlist

- client = OpenAI(api_key="sk-...")
+ client = Onlist(api_key="sk-...")

Migration from OpenRouter

Drop the baseURL override entirely.

- from openai import OpenAI
+ from onlist import Onlist

- client = OpenAI(
-     base_url="https://openrouter.ai/api/v1",
-     api_key=os.environ["OPENROUTER_API_KEY"],
- )
+ client = Onlist()