MCP Character Tools

Instructions

Implementation Reference

• src/tools/counting.ts:191-219 (handler)

  The core handler function that implements the letter frequency analysis logic, processing the input text according to options and computing frequency distribution, most/least common characters.
  export function letterFrequency(input: LetterFrequencyInput): LetterFrequencyOutput { const { text, case_sensitive, include_spaces, include_punctuation, letters_only } = input; const frequency: Record<string, number> = {}; const processedText = case_sensitive ? text : text.toLowerCase(); for (const char of processedText) { // Filter based on options if (letters_only && !/[a-zA-Z]/.test(char)) continue; if (!include_spaces && char === ' ') continue; if (!include_punctuation && /[^\w\s]/.test(char)) continue; frequency[char] = (frequency[char] || 0) + 1; } const entries = Object.entries(frequency).sort((a, b) => b[1] - a[1]); const most_common = entries.slice(0, 5).map(([char, count]) => ({ char, count })); const least_common = entries.slice(-5).reverse().map(([char, count]) => ({ char, count })); return { text, total_characters: Object.values(frequency).reduce((a, b) => a + b, 0), unique_characters: Object.keys(frequency).length, frequency, frequency_table: formatFrequencyTable(frequency), most_common, least_common, }; }
• src/tools/counting.ts:173-189 (schema)

  TypeScript interfaces defining the input parameters and output structure for the letterFrequency handler.
  export interface LetterFrequencyInput { text: string; case_sensitive: boolean; include_spaces: boolean; include_punctuation: boolean; letters_only: boolean; } export interface LetterFrequencyOutput { text: string; total_characters: number; unique_characters: number; frequency: Record<string, number>; frequency_table: string; most_common: Array<{ char: string; count: number }>; least_common: Array<{ char: string; count: number }>; }
• src/index.ts:166-205 (registration)

  MCP server registration of the 'letter_frequency' tool, including Zod input schema validation and wrapper that calls the handler and formats response.
  server.registerTool( "letter_frequency", { title: "Letter Frequency", description: `Get frequency distribution of all characters in text. Provides a complete breakdown of character frequencies. Args: - text (string): The text to analyze - case_sensitive (boolean): Distinguish upper/lowercase (default: false) - include_spaces (boolean): Include spaces in count (default: false) - include_punctuation (boolean): Include punctuation (default: false) - letters_only (boolean): Only count a-z letters (default: true) Returns: Frequency map, sorted list, most/least common characters. Example: letter_frequency("hello") → h: 1, e: 1, l: 2, o: 1`, inputSchema: z.object({ text: z.string().min(1).describe("The text to analyze"), case_sensitive: z.boolean().default(false).describe("Distinguish upper/lowercase"), include_spaces: z.boolean().default(false).describe("Include spaces"), include_punctuation: z.boolean().default(false).describe("Include punctuation"), letters_only: z.boolean().default(true).describe("Only count a-z letters"), }).strict(), annotations: { readOnlyHint: true, destructiveHint: false, idempotentHint: true, openWorldHint: false }, }, async (params) => { const result = letterFrequency({ text: params.text, case_sensitive: params.case_sensitive, include_spaces: params.include_spaces, include_punctuation: params.include_punctuation, letters_only: params.letters_only, }); return { content: [{ type: "text" as const, text: `Frequency analysis of "${result.text}":\n\n${result.frequency_table}\n\nMost common: ${result.most_common.map(c => `'${c.char}': ${c.count}`).join(', ')}` }], }; } );