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ReferenceEvalsToneConsistency

ToneConsistencyMetric

The ToneConsistencyMetric class evaluates the text’s emotional tone and sentiment consistency. It can operate in two modes: comparing tone between input/output pairs or analyzing tone stability within a single text.

Basic Usage

import { ToneConsistencyMetric } from "@mastra/evals/nlp";
 
const metric = new ToneConsistencyMetric();
 
// Compare tone between input and output
const result1 = await metric.measure(
  "I love this amazing product!",
  "This product is wonderful and fantastic!"
);
 
// Analyze tone stability in a single text
const result2 = await metric.measure(
  "The service is excellent. The staff is friendly. The atmosphere is perfect.",
  ""  // Empty string for single-text analysis
);
 
console.log(result1.score); // Tone consistency score from 0-1
console.log(result2.score); // Tone stability score from 0-1

measure() Parameters

input:

string
The text to analyze for tone

output:

string
Reference text for tone comparison (empty string for stability analysis)

Returns

score:

number
Tone consistency/stability score (0-1)

info:

object
Detailed tone info

info Object (Tone Comparison)

responseSentiment:

number
Sentiment score for the input text

referenceSentiment:

number
Sentiment score for the output text

difference:

number
Absolute difference between sentiment scores

info Object (Tone Stability)

avgSentiment:

number
Average sentiment score across sentences

sentimentVariance:

number
Variance in sentiment between sentences

Scoring Details

The metric evaluates sentiment consistency through tone pattern analysis and mode-specific scoring.

Scoring Process

  1. Analyzes tone patterns:

    • Extracts sentiment features
    • Computes sentiment scores
    • Measures tone variations

  2. Calculates mode-specific score: Tone Consistency (input and output):

    • Compares sentiment between texts
    • Calculates sentiment difference
    • Score = 1 - (sentiment_difference / max_difference)

    Tone Stability (single input):

    • Analyzes sentiment across sentences
    • Calculates sentiment variance
    • Score = 1 - (sentiment_variance / max_variance)

Final score: mode_specific_score * scale

Score interpretation

(0 to scale, default 0-1)

  • 1.0: Perfect tone consistency/stability
  • 0.7-0.9: Strong consistency with minor variations
  • 0.4-0.6: Moderate consistency with noticeable shifts
  • 0.1-0.3: Poor consistency with major tone changes
  • 0.0: No consistency - completely different tones

Example with Both Modes

import { ToneConsistencyMetric } from "@mastra/evals/nlp";
 
const metric = new ToneConsistencyMetric();
 
// Tone Consistency Mode
const consistencyResult = await metric.measure(
  "This product is fantastic and amazing!",
  "The product is excellent and wonderful!"
);
// Example output:
// {
//   score: 0.95,
//   info: {
//     responseSentiment: 0.8,
//     referenceSentiment: 0.75,
//     difference: 0.05
//   }
// }
 
// Tone Stability Mode
const stabilityResult = await metric.measure(
  "Great service! Friendly staff. Perfect atmosphere.",
  ""
);
// Example output:
// {
//   score: 0.9,
//   info: {
//     avgSentiment: 0.6,
//     sentimentVariance: 0.1
//   }
// }
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