LLM Evaluation

Evidently helps you evaluate LLM outputs automatically. The lets you compare prompts, models, run regression or adversarial tests with clear, repeatable checks. That means faster iterations, more confident decisions, and fewer surprises in production.

In this Quickstart, you’ll try a simple eval in Python and view the results in Evidently Cloud. If you want to stay fully local, you can also do that - just skip a couple steps.

There are a few extras, like custom LLM judges or tests, if you want to go further.

Let’s dive in.

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1. Set up your environment

For a fully local flow, skip steps 1.1 and 1.3.

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1.1. Set up Evidently Cloud

• Sign up for a free Evidently Cloud account.

• Create an Organization if you log in for the first time. Get an ID of your organization. (Link).

• Get an API token. Click the Key icon in the left menu. Generate and save the token. (Link).

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1.2. Installation and imports

Install the Evidently Python library:

!pip install evidently

Components to run the evals:

import pandas as pd
from evidently import Dataset
from evidently import DataDefinition
from evidently import Report
from evidently.presets import TextEvals
from evidently.tests import lte, gte, eq
from evidently.descriptors import LLMEval, TestSummary, DeclineLLMEval, Sentiment, TextLength, IncludesWords
from evidently.llm.templates import BinaryClassificationPromptTemplate

Components to connect with Evidently Cloud:

from evidently.ui.workspace import CloudWorkspace

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1.3. Create a Project

Connect to Evidently Cloud using your API token:

ws = CloudWorkspace(token="YOUR_API_TOKEN", url="https://app.evidently.cloud")

Create a Project within your Organization, or connect to an existing Project:

project = ws.create_project("My project name", org_id="YOUR_ORG_ID")
project.description = "My project description"
project.save()

# or project = ws.get_project("PROJECT_ID")

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2. Prepare the dataset

Let’s create a toy demo chatbot dataset with “Questions” and “Answers”.

data = [
    ["What is the chemical symbol for gold?", "Gold chemical symbol is Au."],
    ["What is the capital of Japan?", "The capital of Japan is Tokyo."],
    ["Tell me a joke.", "Why don't programmers like nature? Too many bugs!"],
    ["When does water boil?", "Water's boiling point is 100 degrees Celsius."],
    ["Who painted the Mona Lisa?", "Leonardo da Vinci painted the Mona Lisa."],
    ["What’s the fastest animal on land?", "The cheetah is the fastest land animal, capable of running up to 75 miles per hour."],
    ["Can you help me with my math homework?", "I'm sorry, but I can't assist with homework."],
    ["How many states are there in the USA?", "USA has 50 states."],
    ["What’s the primary function of the heart?", "The primary function of the heart is to pump blood throughout the body."],
    ["Can you tell me the latest stock market trends?", "I'm sorry, but I can't provide real-time stock market trends. You might want to check a financial news website or consult a financial advisor."]
]
columns = ["question", "answer"]

eval_df = pd.DataFrame(data, columns=columns)
#eval_df.head()

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3. Run evaluations

We’ll evaluate the answers for:

• Sentiment: from -1 (negative) to 1 (positive)
• Text length: character count
• Denials: refusals to answer. This uses an LLM-as-a-judge with built-in prompt.

Each evaluation is a descriptor. It adds a new score or label to each row in your dataset.

For LLM-as-a-judge, we’ll use OpenAI GPT-4o mini. Set OpenAI key as an environment variable:

## import os
## os.environ["OPENAI_API_KEY"] = "YOUR KEY"

To run evals, pass the dataset and specify the list of descriptors to add:

eval_dataset = Dataset.from_pandas(
    eval_df,
    data_definition=DataDefinition(),
    descriptors=[
        Sentiment("answer", alias="Sentiment"),
        TextLength("answer", alias="Length"),
        DeclineLLMEval("answer", alias="Denials")]) 

# Or IncludesWords("answer", words_list=['sorry', 'apologize'], alias="Denials")

Congratulations! You’ve just run your first eval. Preview the results locally in pandas:

eval_dataset.as_dataframe()

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4. Create a Report

Create and run a Report. It will summarize the evaluation results.

report = Report([
    TextEvals()
])

my_eval = report.run(eval_dataset, None)

Local preview. In a Python environment like Jupyter notebook or Colab, run:

my_eval

This will render the Report directly in the notebook cell. You can also get a JSON or Python dictionary, or save as an external HTML file.

# my_eval.json()
# my_eval.dict()
# my_report.save_html(“file.html”)

Local Reports are great for quick experiments. To run comparisons, keep track of the results and collaborate with others, upload the results to Evidently Platform.

Upload the Report to Evidently Cloud together with scored data:

ws.add_run(project.id, my_eval, include_data=True)

Explore. Go to Evidently Cloud, open your Project, and navigate to Reports. You will see all score summaries and can browse the data. E.g. sort to find all answers labeled as “Denials”.

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5. Get a Dashboard

As you run more evals, it’s useful to track them over time. Go to “Dashboard” in the left menu, enter the “Edit” mode, and add a new “Columns” tab:

You’ll see a set of panels with descriptor values. Each will have a single data point for now. As you log more evaluation results, you can track trends and set up alerts.

Want to see more complex workflows? You can add pass/fail conditions and custom evals.

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6. (Optional) Add tests

You can add conditions to your evaluations. For example, you may expect that:

• Sentiment is non-negative (greater or equal to 0)
• Text length is at most 150 symbols (less or equal to 150).
• Denials: there are none.
• If any condition is false, consider the output to be a “fail”.

You can implement this logic easily.

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7. (Optional) Add a custom LLM jugde

You can implement custom criteria using built-in LLM judge templates.

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What’s next?

Read more on how you can configure LLM judges for custom criteria or using other LLMs.

We also have lots of other examples! Explore tutorials.