MySql MCP Server

Instructions

Implementation Reference

• src/index.ts:431-452 (handler)

  The handler for the "list_tables" tool within the CallToolRequestSchema switch statement. It executes a "SHOW TABLES" query using the shared executeQuery function and returns the result as JSON or an error message.

  case "list_tables": {
    try {
      const rows = await executeQuery("SHOW TABLES");
      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:203-216 (registration)

  Registration of the "list_tables" tool in the ListToolsRequestSchema response. Includes the tool name, description, and input schema definition (using a dummy parameter since no real inputs are needed).

  {
    name: "list_tables",
    description: "Get a list of tables in the current database.",
    inputSchema: {
      type: "object",
      properties: {
        random_string: {
          type: "string",
          description: "Dummy parameter for no-parameter tools"
        }
      },
      required: ["random_string"]
    }
  },

• src/index.ts:206-215 (schema)

  Input schema for the "list_tables" tool, which requires a dummy 'random_string' parameter as it's a no-parameter tool.

  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 the list_tables handler to safely execute the SQL query, including read-only mode 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;
  }