const z = require('zod/v4');
const textLengthToolInstructions = [
'Use estimate-text-length-difference to compare original vs translated text lengths and flag large deltas.',
'Configure tolerancePercent to set the allowed absolute percentage difference (default 30%).',
'The tool reports both lengths, percent change, and whether the change exceeds tolerance.'
].join('\n');
const lengthDiffInputSchema = z.object({
sourceText: z.string().min(1).describe('Original text before translation'),
translatedText: z.string().min(1).describe('Translated text to compare against the original'),
tolerancePercent: z
.number()
.min(1)
.max(500)
.default(30)
.describe('Allowed absolute percent difference between lengths before flagging risk')
});
function measureLength(text) {
return Array.from(text).length;
}
function registerTextLengthTool(server) {
server.registerTool(
'estimate-text-length-difference',
{
title: 'Estimate text length difference',
description:
'Compare original and translated text lengths to detect layout risk; configurable tolerancePercent (default 30%).',
inputSchema: lengthDiffInputSchema
},
async params => {
const sourceLength = measureLength(params.sourceText);
const translatedLength = measureLength(params.translatedText);
const delta = translatedLength - sourceLength;
const percentChange = sourceLength === 0 ? null : (delta / sourceLength) * 100;
const exceeds =
percentChange === null ? translatedLength > 0 : Math.abs(percentChange) > params.tolerancePercent;
const direction = delta === 0 ? 'no change' : delta > 0 ? 'longer' : 'shorter';
const verdict =
percentChange === null && translatedLength === 0
? '✅ Both texts are empty; no length risk.'
: percentChange === null
? '⚠️ Source length is 0; percent change undefined and translated text is present.'
: exceeds
? '⚠️ Length difference exceeds tolerance (layout risk likely).'
: '✅ Length difference within tolerance.';
const summary = [
verdict,
`Source length: ${sourceLength}`,
`Translated length: ${translatedLength}`,
percentChange === null
? `Change: N/A (source length is 0; direction: ${direction})`
: `Change: ${percentChange.toFixed(2)}% (${direction})`,
`Tolerance: ±${params.tolerancePercent}%`
].join('\n');
return { content: [{ type: 'text', text: summary }] };
}
);
}
module.exports = {
registerTextLengthTool,
textLengthToolInstructions
};
