MySql MCP Server

Instructions

Implementation Reference

• src/index.ts:484-505 (handler)

  Handler for the 'list_databases' tool. Executes 'SHOW DATABASES' query via executeQuery helper and returns the list of databases as JSON, with error handling.

  case "list_databases": {
    try {
      const rows = await executeQuery("SHOW DATABASES");
      return {
        content: [{ type: "text", text: JSON.stringify(rows, null, 2) }],
        isError: false
      };
    } catch (error) {
      return {
        content: [
          {
            type: "text",
            text:
              error instanceof Error
                ? error.message
                : "Unknown error occurred"
          }
        ],
        isError: true
      };
    }
  }

• src/index.ts:231-244 (registration)

  Registration of the 'list_databases' tool in the ListToolsRequestHandler, including name, description, and input schema (dummy param for no-args tool).

  {
    name: "list_databases",
    description: "Get a list of all accessible databases on the server.",
    inputSchema: {
      type: "object",
      properties: {
        random_string: {
          type: "string",
          description: "Dummy parameter for no-parameter tools"
        }
      },
      required: ["random_string"]
    }
  },

• src/index.ts:234-243 (schema)

  Input schema definition for the 'list_databases' tool, requiring a dummy 'random_string' parameter.

  inputSchema: {
    type: "object",
    properties: {
      random_string: {
        type: "string",
        description: "Dummy parameter for no-parameter tools"
      }
    },
    required: ["random_string"]
  }

• src/index.ts:117-133 (helper)

  Shared helper function executeQuery used by list_databases to run the SQL query, includes read-only validation.

  async function executeQuery(sql: string, params: any[] = []): Promise<any> {
    const conn = await getConnection();
  
    // Check if in readonly mode and validate query type
    if (connectionConfig.readonly) {
      const queryType = getQueryType(sql);
      if (isWriteOperation(queryType)) {
        throw new Error(
          "Server is in read-only mode. Write operations are not allowed."
        );
      }
    }
  
    // Execute the query
    const [rows] = await conn.query(sql, params);
    return rows;
  }