Quick start

Getting started with Braintrust

Braintrust helps evaluate your LLM app, so you can quickly and confidently ship to production. We provide a Typescript/Python library to log evaluation experiments and production data.

Install Braintrust libraries

Start by installing the Typescript or Python library.

npm install braintrust autoevals


yarn add braintrust autoevals

Create a simple evaluation script

First, create a simple evaluation script. Make sure to follow the naming conventions for your language. Typescript files should be named *.eval.ts and Python files should be named eval_*.py.

import { Eval } from "braintrust";
import { LevenshteinScorer } from "autoevals";
Eval("Say Hi Bot", {
  data: () => {
    return [
        input: "Foo",
        expected: "Hi Foo",
        input: "Bar",
        expected: "Hello Bar",
    ]; // Replace with your eval dataset
  task: (input) => {
    return "Hi " + input; // Replace with your LLM call
  scores: [LevenshteinScorer],

This script sets up the basic scaffolding of an evaluation:

  • data is an array or iterator of data you'll evaluate
  • task is a function that takes in an input and returns an output
  • scores is an array of scoring functions that will be used to score the tasks's output

Create an API key

Next, create an API key to authenticate your evaluation script. You can create an API key in the settings page.

Run your evaluation script

Run your evaluation script with the following command:

BRAINTRUST_API_KEY=<YOUR_API_KEY> npx braintrust eval tutorial.eval.ts

Once the command runs, you'll see a link to your experiment.

View your results

Congrats, you just ran an eval! You should see a dashboard like this when you load your experiment. This view is called the experiment view, and as you use Braintrust, we hope it becomes your trusty companion each time you change your code and want to run an eval.

The experiment view allows you to look at high level metrics for performance, dig into individual examples, and compare your LLM app's performance over time.

First eval

Run another experiment

Now that you've run your first eval, you'll notice that we only achieved a 77.8% score. Can you improve that?

Second eval

Next Steps