DynamoDB Read-Only MCP

Instructions

Implementation Reference

• src/index.ts:47-76 (registration)

  MCP server.tool registration for 'describe-table', defining name, description, input schema, and thin async handler that calls describeTable and formats response.

  server.tool(
    'describe-table',
    'Get detailed information about a DynamoDB table',
    {
      tableName: z.string().describe('Name of the table to get details for'),
    },
    async ({ tableName }) => {
      try {
        const tableInfo = await describeTable(tableName);
        return {
          content: [
            {
              type: 'text',
              text: JSON.stringify(tableInfo, null, 2),
            },
          ],
        };
      } catch (error: any) {
        return {
          isError: true,
          content: [
            {
              type: 'text',
              text: `Error occurred: ${error.message}`,
            },
          ],
        };
      }
    }
  );

• src/dynamo-helpers.ts:21-35 (handler)

  Core handler logic: creates DescribeTableCommand with tableName and sends it to DynamoDB client, returning the Table description or throwing error.

  export async function describeTable(tableName: string) {
    console.error('# Starting describeTable function:', tableName);
    try {
      const command = new DescribeTableCommand({
        TableName: tableName,
      });
      console.error('# DescribeTable command created successfully');
      const response = await dynamodb.send(command);
      console.error('# DescribeTable response received:', response);
      return response.Table;
    } catch (error) {
      console.error('# Error in describeTable function:', error);
      throw error;
    }
  }

• src/index.ts:50-52 (schema)

  Zod input schema defining 'tableName' as required string parameter.

  {
    tableName: z.string().describe('Name of the table to get details for'),
  },

• src/dynamo-client.ts:19-32 (helper)

  Helper function to initialize and provide the DynamoDBDocumentClient instance used by describeTable.

  export const getDynamodb = (): DynamoDBDocumentClient => {
    if (!dynamoDbDocClient) {
      dynamoDbClient = new DynamoDBClient({
        region: process.env.AWS_REGION || 'ap-northeast-2',
        credentials: {
          accessKeyId: process.env.AWS_ACCESS_KEY_ID || '',
          secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY || '',
          sessionToken: process.env.AWS_SESSION_TOKEN || undefined, // Optional, only if using temporary credentials
        },
      });
      dynamoDbDocClient = DynamoDBDocumentClient.from(dynamoDbClient);
    }
    return dynamoDbDocClient;
  };