count-items
Count items in a DynamoDB table using optional filters to retrieve specific data. Ideal for tracking table sizes or applying conditional queries in read-only operations.
Instructions
Count items in a DynamoDB table
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| expressionAttributeValues | No | Filter expression attribute values (optional) | |
| filterExpression | No | Filter expression (optional) | |
| tableName | Yes | Table name |
Implementation Reference
- src/dynamo-helpers.ts:195-231 (handler)Core handler function that executes the item counting logic by performing a DynamoDB Scan operation with Select: 'COUNT' and optional filters.
export async function countItems( tableName: string, filterExpression?: string, expressionAttributeValues?: Record<string, any> ) { console.error('# Starting countItems function:', { tableName, filterExpression, expressionAttributeValues, }); try { const params: any = { TableName: tableName, Select: 'COUNT', }; if (filterExpression) { params.FilterExpression = filterExpression; } if (expressionAttributeValues) { params.ExpressionAttributeValues = expressionAttributeValues; } console.error('# Count parameters:', params); const command = new ScanCommand(params); console.error('# Count command created successfully'); const response = await dynamodb.send(command); console.error('# Count response received:', response); return response.Count || 0; } catch (error) { console.error('# Error in countItems function:', error); throw error; } } - src/index.ts:294-328 (registration)Registers the 'count-items' tool with the MCP server, defines the input schema using Zod, and provides a thin wrapper handler that calls the core countItems function and formats the MCP response.
server.tool( 'count-items', 'Count items in a DynamoDB table', { tableName: z.string().describe('Table name'), filterExpression: z.string().optional().describe('Filter expression (optional)'), expressionAttributeValues: z .record(z.any()) .optional() .describe('Filter expression attribute values (optional)'), }, async ({ tableName, filterExpression, expressionAttributeValues }) => { try { const count = await countItems(tableName, filterExpression, expressionAttributeValues); return { content: [ { type: 'text', text: `Table "${tableName}" has ${count} items.`, }, ], }; } catch (error: any) { return { isError: true, content: [ { type: 'text', text: `Error occurred: ${error.message}`, }, ], }; } } ); - src/index.ts:297-303 (schema)Zod schema defining the input parameters for the 'count-items' tool.
{ tableName: z.string().describe('Table name'), filterExpression: z.string().optional().describe('Filter expression (optional)'), expressionAttributeValues: z .record(z.any()) .optional() .describe('Filter expression attribute values (optional)'),