Calculate

Instructions

Implementation Reference

• src/server.ts:58-93 (handler)

  The calculate tool handler: validates args, performs arithmetic operation (add, subtract, multiply, divide), and returns formatted result as text content.

  async (args: { [x: string]: any }) => {
    const { operation, a, b }: CalculateArgs = validateToolArgs(
      CalculateSchema,
      args
    );
  
    let result: number;
    switch (operation) {
      case 'add':
        result = a + b;
        break;
      case 'subtract':
        result = a - b;
        break;
      case 'multiply':
        result = a * b;
        break;
      case 'divide':
        result = a / b;
        break;
      default:
        // This should never happen due to Zod validation, but keeping for safety
        throw new Error(
          `Unknown operation: ${operation}. Supported: add, subtract, multiply, divide`
        );
    }
  
    return {
      content: [
        {
          type: 'text',
          text: `${a} ${operation} ${b} = ${result}`,
        },
      ],
    };
  }

• src/schemas/toolSchemas.ts:20-43 (schema)

  Zod schema defining CalculateArgs: operation enum, numbers a/b, with refinement to prevent division by zero.

  export const CalculateSchema = z
    .object({
      operation: z
        .enum(['add', 'subtract', 'multiply', 'divide'], {
          errorMap: () => ({
            message: 'Operation must be one of: add, subtract, multiply, divide',
          }),
        })
        .describe('The arithmetic operation to perform'),
      a: z.number().describe('First number for the calculation'),
      b: z.number().describe('Second number for the calculation'),
    })
    .refine(
      data => {
        if (data.operation === 'divide' && data.b === 0) {
          return false;
        }
        return true;
      },
      {
        message: 'Division by zero is not allowed',
        path: ['b'],
      }
    );

• src/server.ts:51-94 (registration)

  Registers the 'calculate' tool on the MCP server with title, description, and handler function.

  server.registerTool(
    'calculate',
    {
      title: 'Calculate',
      description:
        'Performs basic arithmetic calculations (add, subtract, multiply, divide)',
    },
    async (args: { [x: string]: any }) => {
      const { operation, a, b }: CalculateArgs = validateToolArgs(
        CalculateSchema,
        args
      );
  
      let result: number;
      switch (operation) {
        case 'add':
          result = a + b;
          break;
        case 'subtract':
          result = a - b;
          break;
        case 'multiply':
          result = a * b;
          break;
        case 'divide':
          result = a / b;
          break;
        default:
          // This should never happen due to Zod validation, but keeping for safety
          throw new Error(
            `Unknown operation: ${operation}. Supported: add, subtract, multiply, divide`
          );
      }
  
      return {
        content: [
          {
            type: 'text',
            text: `${a} ${operation} ${b} = ${result}`,
          },
        ],
      };
    }
  );

• src/schemas/toolSchemas.ts:65-77 (helper)

  Utility function to validate tool arguments using Zod schema with custom error formatting, used in calculate handler.

  export function validateToolArgs<T>(schema: z.ZodSchema<T>, args: unknown): T {
    try {
      return schema.parse(args);
    } catch (error) {
      if (error instanceof z.ZodError) {
        const errorMessages = error.errors
          .map(err => `${err.path.join('.')}: ${err.message}`)
          .join(', ');
        throw new Error(`Validation failed: ${errorMessages}`);
      }
      throw error;
    }
  }