Context recall scorer

The createContextRecallScorer() function creates a scorer that evaluates how well retrieved context covers the claims in a ground-truth reference answer. It measures retrieval completeness by checking what fraction of the ground truth's claims are attributable to the retrieved context.

This scorer requires a ground-truth reference answer, making it suitable for labeled datasets in CI or test environments. When groundTruth is not provided in the run, the scorer returns a score of 0 rather than throwing an error.

RAG retrieval evaluation

Ideal for evaluating retrieval completeness in RAG pipelines where:

• You need to verify the retriever fetches all necessary information
• You have labeled datasets with known-correct answers
• You want to catch regressions in what the retriever returns

Dataset-driven testing

Use when running evaluations against curated test sets:

• CI pipelines with ground-truth labeled questions
• A/B testing retrieval strategies
• Benchmarking embedding models for coverage

Parameters

model:

MastraModelConfig

The language model to use for evaluating claim attribution

options:

ContextRecallMetricOptions

Configuration options for the scorer

Note: Either context or contextExtractor must be provided. When both are provided, contextExtractor is used only if the run input and output are agent-shaped (MastraDBMessage[]); otherwise the scorer falls back to context.

.run() returns

score:

number

Recall score between 0 and scale (default 0-1), representing the fraction of ground-truth claims covered by the context

reason:

string

Human-readable explanation of which ground-truth claims were and were not found in the context

Scoring details

Claim attribution

Context Recall uses a two-step LLM evaluation followed by a deterministic score calculation:

1. Claim extraction: The ground-truth answer is decomposed into atomic claims
2. Attribution check: Each claim is checked against the retrieval context for support

The score is then calculated as the ratio of attributed claims to total claims, multiplied by scale.

Scoring formula

Context Recall = attributed_claims / total_claims × scale

Where:
- attributed_claims = number of ground-truth claims supported by the context
- total_claims = total number of claims extracted from the ground truth
- Attribution is binary: a claim is either supported (yes) or not (no)

Score interpretation

These ranges assume the default scale of 1. When using a custom scale, multiply accordingly.

• 0.9-1.0: Excellent recall — context covers nearly all ground-truth claims
• 0.7-0.8: Good recall — most claims are covered, minor gaps
• 0.4-0.6: Moderate recall — significant information missing from context
• 0.1-0.3: Poor recall — most ground-truth claims not found in context
• 0.0: No recall — none of the ground-truth claims are in the context

Reason analysis

The reason field explains:

• Which ground-truth claims were found in the context
• Which claims were missing and what information gaps exist
• Specific context pieces that supported attributed claims

Optimization insights

Use results to:

• Improve retrieval: Identify what types of information the retriever misses
• Tune chunk size: Ensure chunks contain enough detail to cover ground-truth claims
• Evaluate embeddings: Test different embedding models for better information coverage
• Expand knowledge base: Add documents that cover frequently missed claims

Example calculation

Given ground truth: "Einstein was born in 1879. He developed relativity. He won the Nobel Prize."

Claims extracted: 3

• "Einstein was born in 1879" → attributed (context mentions birthdate)
• "Einstein developed relativity" → attributed (context covers relativity)
• "Einstein won the Nobel Prize" → not attributed (context doesn't mention Nobel Prize)

Recall = 2/3 = 0.67

Scorer configuration

Dynamic context extraction

const scorer = createContextRecallScorer({
  model: 'openai/gpt-5.5',
  options: {
    contextExtractor: (input, output) => {
      const query = input?.inputMessages?.[0]?.content || ''
      const searchResults = vectorDB.search(query, { limit: 10 })
      return searchResults.map(result => result.content)
    },
    scale: 1,
  },
})

Static context evaluation

const scorer = createContextRecallScorer({
  model: 'openai/gpt-5.5',
  options: {
    context: [
      'Document 1: Einstein was born on 14 March 1879 in Ulm, Germany.',
      'Document 2: Einstein published the theory of special relativity in 1905.',
      'Document 3: Einstein moved to the United States in 1933.',
    ],
  },
})

Example

Evaluate RAG retrieval completeness against a labeled dataset:

src/example-context-recall.ts

import { runEvals } from '@mastra/core/evals'
import { createContextRecallScorer } from '@mastra/evals/scorers/prebuilt'
import { myAgent } from './agent'

const scorer = createContextRecallScorer({
  model: 'openai/gpt-5.5',
  options: {
    contextExtractor: (input, output) => {
      // Extract context from tool invocation results in the agent output
      return output
        .filter(msg => msg?.role === 'assistant')
        .flatMap(msg => msg?.content?.toolInvocations ?? [])
        .filter((tool: any) => tool.state === 'result')
        .map((tool: any) => JSON.stringify(tool.result))
    },
  },
})

const result = await runEvals({
  data: [
    {
      input: 'What are the health benefits of green tea?',
      groundTruth:
        'Green tea contains antioxidants that reduce inflammation, L-theanine that improves focus, and catechins that boost metabolism.',
    },
    {
      input: 'How does photosynthesis work?',
      groundTruth:
        'Photosynthesis converts sunlight into chemical energy using chlorophyll in chloroplasts, producing glucose and oxygen from carbon dioxide and water.',
    },
  ],
  scorers: [scorer],
  target: myAgent,
  onItemComplete: ({ scorerResults }) => {
    console.log({
      score: scorerResults[scorer.id].score,
      reason: scorerResults[scorer.id].reason,
    })
  },
})

console.log(result.scores)

For more details on runEvals, see the runEvals reference.

To add this scorer to an agent, see the Scorers overview guide.

Comparison with context precision

Choose the right scorer for your needs:

Use case	Context Recall	Context Precision
What it measures	Coverage of ground truth	Relevance of retrieved chunks
Direction	Ground truth → context	Context → ground truth
Position sensitive	No	Yes (rewards early placement)
Requires ground truth	Yes	Yes
Failure mode caught	Missing information	Irrelevant noise

Use both together for a complete picture of retrieval quality: precision catches junk in the context, recall catches gaps.

Related

• Context Precision Scorer: Evaluates if retrieved context is relevant and well-ranked
• Context Relevance Scorer: Evaluates context usage and quality
• Faithfulness Scorer: Measures answer groundedness in context
• Custom Scorers: Creating your own evaluation metrics