MCP Character Tools

Instructions

Implementation Reference

• src/tools/analysis.ts:38-94 (handler)

  The core handler function `compareTexts` that executes the tool's logic: computes letter frequencies for both texts using `letterFrequency`, determines common/unique characters, frequency differences, Jaccard similarity score, and generates a summary.
  export function compareTexts(input: CompareTextsInput): CompareTextsOutput { const { text1, text2, case_sensitive } = input; const freq1 = letterFrequency({ text: text1, case_sensitive, include_spaces: false, include_punctuation: false, letters_only: true, }); const freq2 = letterFrequency({ text: text2, case_sensitive, include_spaces: false, include_punctuation: false, letters_only: true, }); const chars1 = new Set(Object.keys(freq1.frequency)); const chars2 = new Set(Object.keys(freq2.frequency)); const common_characters = [...chars1].filter(c => chars2.has(c)).sort(); const unique_to_text1 = [...chars1].filter(c => !chars2.has(c)).sort(); const unique_to_text2 = [...chars2].filter(c => !chars1.has(c)).sort(); const allChars = new Set([...chars1, ...chars2]); const frequency_comparison: FrequencyComparison[] = [...allChars] .sort() .map(char => ({ char, count_in_text1: freq1.frequency[char] || 0, count_in_text2: freq2.frequency[char] || 0, difference: (freq1.frequency[char] || 0) - (freq2.frequency[char] || 0), })); // Calculate Jaccard similarity const intersection = common_characters.length; const union = allChars.size; const similarity_score = union > 0 ? Math.round((intersection / union) * 100) : 0; const summary = `Text1 (${text1.length} chars) and Text2 (${text2.length} chars) share ${common_characters.length} common characters. Similarity: ${similarity_score}%.`; return { text1, text2, text1_length: text1.length, text2_length: text2.length, case_sensitive, common_characters, unique_to_text1, unique_to_text2, frequency_comparison, similarity_score, summary, }; }
• src/tools/analysis.ts:11-36 (schema)

  TypeScript interfaces defining the input (CompareTextsInput), supporting types (FrequencyComparison), and output (CompareTextsOutput) for the compare_texts tool.
  export interface CompareTextsInput { text1: string; text2: string; case_sensitive: boolean; } export interface FrequencyComparison { char: string; count_in_text1: number; count_in_text2: number; difference: number; } export interface CompareTextsOutput { text1: string; text2: string; text1_length: number; text2_length: number; case_sensitive: boolean; common_characters: string[]; unique_to_text1: string[]; unique_to_text2: string[]; frequency_comparison: FrequencyComparison[]; similarity_score: number; summary: string; }
• src/index.ts:377-410 (registration)

  Registration of the "compare_texts" tool using McpServer.registerTool, including Zod inputSchema validation, description, and the async handler that calls the compareTexts function and formats the MCP response.
  server.registerTool( "compare_texts", { title: "Compare Texts", description: `Compare letter frequencies between two texts. Useful for analyzing similarity or differences. Args: - text1 (string): First text - text2 (string): Second text - case_sensitive (boolean): Distinguish case (default: false) Returns: Common characters, unique to each, frequency comparison, similarity score. Example: compare_texts("hello", "world") → common: ['l', 'o'], unique_to_text1: ['h', 'e'], etc.`, inputSchema: z.object({ text1: z.string().min(1).describe("First text"), text2: z.string().min(1).describe("Second text"), case_sensitive: z.boolean().default(false).describe("Distinguish case"), }).strict(), annotations: { readOnlyHint: true, destructiveHint: false, idempotentHint: true, openWorldHint: false }, }, async (params) => { const result = compareTexts({ text1: params.text1, text2: params.text2, case_sensitive: params.case_sensitive, }); return { content: [{ type: "text" as const, text: `${result.summary}\n\nCommon: [${result.common_characters.join(', ')}]\nOnly in text1: [${result.unique_to_text1.join(', ')}]\nOnly in text2: [${result.unique_to_text2.join(', ')}]` }], }; } );