Database Tools for Claude AI

Instructions

Implementation Reference

• index.js:18-38 (registration)

  Registers the 'mysql' tool on the MCP server with description, input schema using Zod, and an async handler function that invokes executeMysqlQuery with environment-based database config.

  server.tool("mysql", "Execute a query in MySQL", {
      query: z.string().describe("SQL query to execute"),
  }, async ({ query }) => {
      try {
          return executeMysqlQuery(query, {
              host: process.env.DB_HOST || 'localhost',
              user: process.env.DB_USER || 'root',
              password: process.env.DB_PASSWORD || ''
          });
      }
      catch (error) {
          return {
              content: [
                  {
                      type: "text",
                      text: "Error executing query: " + (error.message || "Unknown error"),
                  },
              ],
          };
      }
  });

• index.js:19-19 (schema)

  Zod schema defining the input parameter 'query' as a string for the mysql tool.

  query: z.string().describe("SQL query to execute"),

• index.js:20-37 (handler)

  The handler function for the mysql tool. It catches errors and calls the executeMysqlQuery helper with config from process.env.

  }, async ({ query }) => {
      try {
          return executeMysqlQuery(query, {
              host: process.env.DB_HOST || 'localhost',
              user: process.env.DB_USER || 'root',
              password: process.env.DB_PASSWORD || ''
          });
      }
      catch (error) {
          return {
              content: [
                  {
                      type: "text",
                      text: "Error executing query: " + (error.message || "Unknown error"),
                  },
              ],
          };
      }

• mysql.js:4-34 (handler)

  Core handler logic: creates MySQL connection using mysql2/promise, executes the query, formats results as JSON string, returns structured content.

  export const executeMysqlQuery = async (query, config) => {
  
      const connection = await mysql.createConnection(config);
  
      const [results] = await connection.execute(query);
  
      await connection.end();
  
      let resultText;
  
      if (Array.isArray(results)) {
          if (results.length === 0) {
              resultText = "The query returned no results.";
          }
          else {
              resultText = `Results (${results.length} rows):\n\n${JSON.stringify(results, null, 2)}`;
          }
      }
      else {
          resultText = `Result: ${JSON.stringify(results, null, 2)}`;
      }
  
      return {
          content: [
              {
                  type: "text",
                  text: resultText,
              },
          ],
      };
  };