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Tone Consistency Scorer

The createToneScorer() function 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.

Parameters​

The createToneScorer() function does not take any options.

This function returns an instance of the MastraScorer class. See the MastraScorer reference for details on the .run() method and its input/output.

.run() Returns​

runId:

string
The id of the run (optional).

analyzeStepResult:

object
Object with tone metrics: { responseSentiment: number, referenceSentiment: number, difference: number } (for comparison mode) OR { avgSentiment: number, sentimentVariance: number } (for stability mode)

score:

number
Tone consistency/stability score (0-1).

.run() returns a result in the following shape:

{
  runId: string,
  analyzeStepResult: {
    responseSentiment?: number,
    referenceSentiment?: number,
    difference?: number,
    avgSentiment?: number,
    sentimentVariance?: number,
  },
  score: number
}

Scoring Details​

The scorer 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

analyzeStepResult​

Object with tone metrics:

  • responseSentiment: Sentiment score for the response (comparison mode).
  • referenceSentiment: Sentiment score for the input/reference (comparison mode).
  • difference: Absolute difference between sentiment scores (comparison mode).
  • avgSentiment: Average sentiment across sentences (stability mode).
  • sentimentVariance: Variance of sentiment across sentences (stability mode).

Examples​

Positive tone example​

In this example, the texts exhibit a similar positive sentiment. The scorer measures the consistency between the tones, resulting in a high score.

src/example-positive-tone.ts
import { createToneScorer } from "@mastra/evals/scorers/code";

const scorer = createToneScorer();

const input = "This product is fantastic and amazing!";
const output = "The product is excellent and wonderful!";

const result = await scorer.run({
  input: [{ role: "user", content: input }],
  output: { role: "assistant", text: output },
});

console.log("Score:", result.score);
console.log("AnalyzeStepResult:", result.analyzeStepResult);

Positive tone output​

The scorer returns a high score reflecting strong sentiment alignment. The analyzeStepResult field provides sentiment values and the difference between them.

{
  score: 0.8333333333333335,
  analyzeStepResult: {
    responseSentiment: 1.3333333333333333,
    referenceSentiment: 1.1666666666666667,
    difference: 0.16666666666666652,
  },
}

Stable tone example​

In this example, the text’s internal tone consistency is analyzed by passing an empty response. This signals the scorer to evaluate sentiment stability within the single input text, resulting in a score reflecting how uniform the tone is throughout.

src/example-stable-tone.ts
import { createToneScorer } from "@mastra/evals/scorers/code";

const scorer = createToneScorer();

const input = "Great service! Friendly staff. Perfect atmosphere.";
const output = "";

const result = await scorer.run({
  input: [{ role: "user", content: input }],
  output: { role: "assistant", text: output },
});

console.log("Score:", result.score);
console.log("AnalyzeStepResult:", result.analyzeStepResult);

Stable tone output​

The scorer returns a high score indicating consistent sentiment throughout the input text. The analyzeStepResult field includes the average sentiment and sentiment variance, reflecting tone stability.

{
  score: 0.9444444444444444,
  analyzeStepResult: {
    avgSentiment: 1.3333333333333333,
    sentimentVariance: 0.05555555555555556,
  },
}

Mixed tone example​

In this example, the input and response have different emotional tones. The scorer picks up on these variations and gives a lower consistency score.

src/example-mixed-tone.ts
import { createToneScorer } from "@mastra/evals/scorers/code";

const scorer = createToneScorer();

const input =
  "The interface is frustrating and confusing, though it has potential.";
const output =
  "The design shows promise but needs significant improvements to be usable.";

const result = await scorer.run({
  input: [{ role: "user", content: input }],
  output: { role: "assistant", text: output },
});

console.log("Score:", result.score);
console.log("AnalyzeStepResult:", result.analyzeStepResult);

Mixed tone output​

The scorer returns a low score due to the noticeable differences in emotional tone. The analyzeStepResult field highlights the sentiment values and the degree of variation between them.

{
  score: 0.4181818181818182,
  analyzeStepResult: {
    responseSentiment: -0.4,
    referenceSentiment: 0.18181818181818182,
    difference: 0.5818181818181818,
  },
}

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