promptfoo--promptfoo/site/docs/configuration/expected-outputs/model-graded/answer-relevance.md

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Answer Relevance	Score LLM response relevance and completeness against user queries using sophisticated AI-powered evaluation metrics

Answer Relevance

The answer-relevance assertion evaluates whether an LLM's output is relevant to the original query. It uses a combination of embedding similarity and LLM evaluation to determine relevance.

How to use it

To use the answer-relevance assertion type, add it to your test configuration like this:

assert:
  - type: answer-relevance
    threshold: 0.7 # Score between 0 and 1

How it works

The answer relevance checker:

1. Uses an LLM to generate potential questions that the output could be answering
2. Compares these questions with the original query using embedding similarity
3. Calculates a relevance score based on the similarity scores

A higher threshold requires the output to be more closely related to the original query.

Example Configuration

Here's a complete example showing how to use answer relevance:

prompts:
  - 'Tell me about {{topic}}'
providers:
  - openai:gpt-5
tests:
  - vars:
      topic: quantum computing
    assert:
      - type: answer-relevance
        threshold: 0.8

Overriding the Providers

Answer relevance uses two types of providers:

• A text provider for generating questions
• An embedding provider for calculating similarity

You can override either or both:

defaultTest:
  options:
    provider:
      text:
        id: gpt-5
        config:
          temperature: 0
      embedding:
        id: openai:text-embedding-ada-002

You can also override providers at the assertion level:

assert:
  - type: answer-relevance
    threshold: 0.8
    provider:
      text: anthropic:claude-2
      embedding: cohere:embed-english-v3.0

Customizing the Prompt

You can customize the question generation prompt using the rubricPrompt property:

defaultTest:
  options:
    rubricPrompt: |
      Given this answer: {{output}}

      Generate 3 questions that this answer would be appropriate for.
      Make the questions specific and directly related to the content.

Further reading

See model-graded metrics for more options.