Use LangChain with a free AI API

Set it up

1. Install the OpenAI integration (pip install langchain-openai, or npm install @langchain/openai).
2. Create a ChatOpenAI client with our base URL and your key.
3. Use it anywhere LangChain expects a chat model: chains, agents, tools.

from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    model="auto",
    base_url="https://www.zerolimitai.com/api/v1",
    api_key="zlai_your_key_here",
)
print(llm.invoke("Say hello in one sentence").content)

import { ChatOpenAI } from "@langchain/openai";

const llm = new ChatOpenAI({
  model: "auto",
  apiKey: "zlai_your_key_here",
  configuration: { baseURL: "https://www.zerolimitai.com/api/v1" },
});
console.log((await llm.invoke("Say hello in one sentence")).content);

Replace zlai_your_key_here with your key. Base URL: https://www.zerolimitai.com/api/v1. LangChain's own documentation

Good to know

• Tool calling (bind_tools / bindTools) is supported.
• Only free models answer, and never through a provider that may train on your prompts. Context is at least 32K tokens, depending on the model.
• Need more than the free tier? Annual ($49/year) gives 2,000 calls a day and Lifetime ($99 once) 10,000. See plans.

If something goes wrong

401 invalid_key

The key is mistyped, revoked or missing the zlai_ prefix. Create a new one in your dashboard under Developer.

404 Not Found

The base URL must end in /api/v1 (https://www.zerolimitai.com/api/v1). Tools add /chat/completions themselves.

429 daily_limit

Your account used its calls for the day. The limit is per account, not per key, and resets at 00:00 UTC; the X-RateLimit-Remaining header shows what is left.

“Model not found”, or a model name you did not choose in the response

Any model ID is accepted: one we do not serve is routed by ZeroOptimize, and the response header X-ZeroOptimize-Substituted-From says what you asked for. Use “auto”.

Slow first word

Some free models think before answering. Keep streaming on so text appears as soon as it is written; a model that stays silent is replaced automatically.

Full reference: API docs · live status

Other tools

Configs checked against each tool's documentation on 2026-10-02.