Implement the Game API and Inventory MCP server

Task 1: Implement the Game API

Before we implement our Game API, we need to create these 5 APIs:

1. saveGame - create or update a game.
2. queryGames - return a paginated list of previously saved games.
3. saveAction - save an action for a given game.
4. queryActions - return a paginated list of all actions related to a game.
5. queryInventory - return a paginated list of items in a player’s inventory.

API schema

To define our API inputs and outputs, let’s create our schema using Zod within the packages/game-api/src/schema directory as follows:

action.ts

import { z } from 'zod';

export const ActionSchema = z.object({
  playerName: z.string(),
  timestamp: z.iso.datetime(),
  role: z.enum(['assistant', 'user']),
  content: z.string(),
});

export type IAction = z.TypeOf<typeof ActionSchema>;

common.ts

import { z } from 'zod';

export const QueryInputSchema = z.object({
  cursor: z.string().optional(),
  limit: z.number().optional().default(100),
});

export const createPaginatedQueryOutput = <ItemType extends z.ZodTypeAny>(
  itemSchema: ItemType,
) => {
  return z.object({
    items: z.array(itemSchema),
    cursor: z.string().nullable(),
  });
};

export type IQueryInput = z.TypeOf<typeof QueryInputSchema>;

game.ts

import { z } from 'zod';

export const GameSchema = z.object({
  playerName: z.string(),
  genre: z.enum(['zombie', 'superhero', 'medieval']),
  lastUpdated: z.iso.datetime(),
});

export type IGame = z.TypeOf<typeof GameSchema>;

inventory.ts

import { z } from 'zod';

export const ItemSchema = z.object({
  playerName: z.string(),
  itemName: z.string(),
  emoji: z.string().optional(),
  lastUpdated: z.iso.datetime(),
  quantity: z.number(),
});

export type IItem = z.TypeOf<typeof ItemSchema>;

index.ts

+

export * from './action.js';
export * from './common.js';
export * from './game.js';
export * from './inventory.js';

+-

export * from './echo.js'
export * from './action.js';
export * from './common.js';
export * from './game.js';
export * from './inventory.js';

You can delete the packages/game-api/src/schema/echo.ts file as we will not be using it in this project.

Tip

For each of the schemas we define in Zod, we also export an interface using the z.TypeOf syntax. This converts our Zod definition into a Typescript interface without having to duplicate effort.

Entity modelling

This is the ER diagram for our application.

We will implement our database in DynamoDB, and will use the ElectroDB DynamoDB client library to simplify things. To install electrodb and the DynamoDB Client, run this command:

pnpm

pnpm add -w electrodb@3.5.0 @aws-sdk/client-dynamodb@3.922.0

yarn

yarn add electrodb@3.5.0 @aws-sdk/client-dynamodb@3.922.0

npm

npm install --legacy-peer-deps electrodb@3.5.0 @aws-sdk/client-dynamodb@3.922.0

bun

bun install electrodb@3.5.0 @aws-sdk/client-dynamodb@3.922.0

Note

All dependencies are added to the root package.json as the @aws/nx-plugin follows the single version policy principle. For more information, refer to the ts#project guide.

To define our ElectroDB entities from the ER Diagram, let’s create the following files within our packages/game-api/src/entities folder:

action.ts

import { Entity } from 'electrodb';
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

export const createActionEntity = (client?: DynamoDBClient) =>
  new Entity(
    {
      model: {
        entity: 'Action',
        version: '1',
        service: 'game',
      },
      attributes: {
        playerName: { type: 'string', required: true, readOnly: true },
        timestamp: {
          type: 'string',
          required: true,
          readOnly: true,
          set: () => new Date().toISOString(),
          default: () => new Date().toISOString(),
        },
        role: { type: 'string', required: true, readOnly: true },
        content: { type: 'string', required: true, readOnly: true },
      },
      indexes: {
        primary: {
          pk: { field: 'pk', composite: ['playerName'] },
          sk: { field: 'sk', composite: ['timestamp'] },
        },
      },
    },
    { client, table: process.env.TABLE_NAME },
  );

game.ts

import { Entity } from 'electrodb';
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

export const createGameEntity = (client?: DynamoDBClient) =>
  new Entity(
    {
      model: {
        entity: 'Game',
        version: '1',
        service: 'game',
      },
      attributes: {
        playerName: { type: 'string', required: true, readOnly: true },
        genre: { type: 'string', required: true, readOnly: true },
        lastUpdated: {
          type: 'string',
          required: true,
          default: () => new Date().toISOString(),
        },
      },
      indexes: {
        primary: {
          pk: { field: 'pk', composite: ['playerName'] },
          sk: {
            field: 'sk',
            composite: [],
          },
        },
      },
    },
    { client, table: process.env.TABLE_NAME },
  );

inventory.ts

import { Entity } from 'electrodb';
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

export const createInventoryEntity = (client?: DynamoDBClient) =>
  new Entity(
    {
      model: {
        entity: 'Inventory',
        version: '1',
        service: 'game',
      },
      attributes: {
        playerName: { type: 'string', required: true, readOnly: true },
        lastUpdated: {
          type: 'string',
          required: true,
          default: () => new Date().toISOString(),
        },
        itemName: {
          type: 'string',
          required: true,
        },
        emoji: {
          type: 'string',
          required: false,
        },
        quantity: {
          type: 'number',
          required: true,
        },
      },
      indexes: {
        primary: {
          pk: { field: 'pk', composite: ['playerName'] },
          sk: { field: 'sk', composite: ['itemName'] },
        },
      },
    },
    { client, table: process.env.TABLE_NAME },
  );

ElectroDB allows us to not only define our types, but can also provide defaults for certain values like timestamps. In addition, ElectroDB follows single-table design which is the best practice when using DynamoDB.

Note

Whilst ElectroDB does support collections, we have chosen not to use them in this tutorial for simplicity.

To prepare for the MCP server to interact with the inventory, let’s ensure we export the inventory entity in packages/game-api/src/index.ts:

packages/game-api/src/index.ts

export type { AppRouter } from './router.js';
export { appRouter } from './router.js';
export type { Context } from './init.js';
export * from './client/index.js';
export * from './schema/index.js';
export * from './entities/inventory.js';

Note

The package structure would be better if we refactored entities into their own shared project so that the MCP server does not need to depend on the API.

Adding the DynamoDB client to our tRPC context

As we need access to the DynamoDB client in each of our procedures, we will create a single instance of the client which we can pass through via context. To do this, make the following changes within packages/game-api/src:

middleware/dynamodb.ts

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { initTRPC } from '@trpc/server';

export interface IDynamoDBContext {
  dynamoDb?: DynamoDBClient;
}

export const createDynamoDBPlugin = () => {
  const t = initTRPC.context<IDynamoDBContext>().create();
  return t.procedure.use(async (opts) => {
    const dynamoDb = new DynamoDBClient();

    const response = await opts.next({
      ctx: {
        ...opts.ctx,
        dynamoDb,
      },
    });

    return response;
  });
};

This is a plugin that we instrument to create the DynamoDBClient and inject it into the context.

middleware/index.ts

import { CreateAWSLambdaContextOptions } from '@trpc/server/adapters/aws-lambda';
import type { APIGatewayProxyEvent } from 'aws-lambda';
import { ILoggerContext } from './logger.js';
import { IMetricsContext } from './metrics.js';
import { ITracerContext } from './tracer.js';
import { IDynamoDBContext } from './dynamodb.js';

export * from './dynamodb.js';
export * from './logger.js';
export * from './metrics.js';
export * from './tracer.js';
export * from './error.js';

export type IMiddlewareContext =
  CreateAWSLambdaContextOptions<APIGatewayProxyEvent> &
    IDynamoDBContext &
    ILoggerContext &
    IMetricsContext &
    ITracerContext;

Augment our IMiddlewareContext to add the IDynamoDBContext.

init.ts

import { initTRPC } from '@trpc/server';
import {
  createDynamoDBPlugin,
  createErrorPlugin,
  createLoggerPlugin,
  createMetricsPlugin,
  createTracerPlugin,
  IMiddlewareContext,
} from './middleware/index.js';

process.env.POWERTOOLS_SERVICE_NAME = 'GameApi';
process.env.POWERTOOLS_METRICS_NAMESPACE = 'GameApi';

export type Context = IMiddlewareContext;

export const t = initTRPC.context<Context>().create();

export const publicProcedure = t.procedure
  .concat(createDynamoDBPlugin())
  .concat(createLoggerPlugin())
  .concat(createTracerPlugin())
  .concat(createMetricsPlugin())
  .concat(createErrorPlugin());

This will instrument the DynamoDB plugin.

Note

The concat api binds our middleware to the procedures we define. For more details please refer to the concat guide.

Defining our procedures

To implement the API methods, make the following changes within packages/game-api/src/procedures:

Queries

query-actions.ts

import { createActionEntity } from '../entities/action.js';
import {
  ActionSchema,
  IAction,
  QueryInputSchema,
  createPaginatedQueryOutput,
} from '../schema/index.js';
import { publicProcedure } from '../init.js';
import { z } from 'zod';

export const queryActions = publicProcedure
  .input(QueryInputSchema.extend({ playerName: z.string() }))
  .output(createPaginatedQueryOutput(ActionSchema))
  .query(async ({ input, ctx }) => {
    const actionEntity = createActionEntity(ctx.dynamoDb);
    const result = await actionEntity.query
      .primary({ playerName: input.playerName })
      .go({ cursor: input.cursor, count: input.limit });

    return {
      items: result.data as IAction[],
      cursor: result.cursor,
    };
  });

query-games.ts

import { createGameEntity } from '../entities/game.js';
import {
  GameSchema,
  IGame,
  QueryInputSchema,
  createPaginatedQueryOutput,
} from '../schema/index.js';
import { publicProcedure } from '../init.js';

export const queryGames = publicProcedure
  .input(QueryInputSchema)
  .output(createPaginatedQueryOutput(GameSchema))
  .query(async ({ input, ctx }) => {
    const gameEntity = createGameEntity(ctx.dynamoDb);
    const result = await gameEntity.scan.go({
      cursor: input.cursor,
      count: input.limit,
    });

    return {
      items: result.data as IGame[],
      cursor: result.cursor,
    };
  });

query-inventory.ts

import {
  ItemSchema,
  QueryInputSchema,
  createPaginatedQueryOutput,
} from '../schema/index.js';
import { publicProcedure } from '../init.js';
import { z } from 'zod';
import { createInventoryEntity } from '../entities/inventory.js';

export const queryInventory = publicProcedure
  .input(QueryInputSchema.extend({ playerName: z.string() }))
  .output(createPaginatedQueryOutput(ItemSchema))
  .query(async ({ input, ctx }) => {
    const inventoryEntity = createInventoryEntity(ctx.dynamoDb);
    const result = await inventoryEntity.query
      .primary({ playerName: input.playerName })
      .go({ cursor: input.cursor, count: input.limit });

    return {
      items: result.data,
      cursor: result.cursor,
    };
  });

Mutations

save-action.ts

import { ActionSchema, IAction } from '../schema/index.js';
import { publicProcedure } from '../init.js';
import { createActionEntity } from '../entities/action.js';
import { createGameEntity } from '../entities/game.js';

export const saveAction = publicProcedure
  .input(ActionSchema.omit({ timestamp: true }))
  .output(ActionSchema)
  .mutation(async ({ input, ctx }) => {
    const actionEntity = createActionEntity(ctx.dynamoDb);
    const gameEntity = createGameEntity(ctx.dynamoDb);

    const action = await actionEntity.put(input).go();
    await gameEntity
      .update({ playerName: input.playerName })
      .set({ lastUpdated: action.data.timestamp })
      .go();
    return action.data as IAction;
  });

save-game.ts

import { createGameEntity } from '../entities/game.js';
import { GameSchema, IGame } from '../schema/index.js';
import { publicProcedure } from '../init.js';

export const saveGame = publicProcedure
  .input(GameSchema.omit({ lastUpdated: true }))
  .output(GameSchema)
  .mutation(async ({ input, ctx }) => {
    const gameEntity = createGameEntity(ctx.dynamoDb);

    const result = await gameEntity.put(input).go();
    return result.data as IGame;
  });

You can delete the echo.ts file (from packages/game-api/src/procedures) as we will not be using it in this project.

Router setup

After we define our procedures, to wire them into our API, update the following file:

packages/game-api/src/router.ts

+

import {
  awsLambdaRequestHandler,
  CreateAWSLambdaContextOptions,
} from '@trpc/server/adapters/aws-lambda';
import { t } from './init.js';
import { APIGatewayProxyEvent } from 'aws-lambda';
import { queryActions } from './procedures/query-actions.js';
import { saveAction } from './procedures/save-action.js';
import { queryGames } from './procedures/query-games.js';
import { saveGame } from './procedures/save-game.js';
import { queryInventory } from './procedures/query-inventory.js';

export const router = t.router;

export const appRouter = router({
  actions: router({
    query: queryActions,
    save: saveAction,
  }),
  games: router({
    query: queryGames,
    save: saveGame,
  }),
  inventory: router({
    query: queryInventory,
  }),
});

export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext: (
    ctx: CreateAWSLambdaContextOptions<APIGatewayProxyEvent>,
  ) => ctx,
  responseMeta: () => ({
    headers: {
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Methods': '*',
    },
  }),
});

export type AppRouter = typeof appRouter;

+-

import {
  awsLambdaRequestHandler,
  CreateAWSLambdaContextOptions,
} from '@trpc/server/adapters/aws-lambda';
import { echo } from './procedures/echo.js';
import { t } from './init.js';
import { APIGatewayProxyEvent } from 'aws-lambda';
import { queryActions } from './procedures/query-actions.js';
import { saveAction } from './procedures/save-action.js';
import { queryGames } from './procedures/query-games.js';
import { saveGame } from './procedures/save-game.js';
import { queryInventory } from './procedures/query-inventory.js';

export const router = t.router;

export const appRouter = router({
  echo,
  actions: router({
    query: queryActions,
    save: saveAction,
  }),
  games: router({
    query: queryGames,
    save: saveGame,
  }),
  inventory: router({
    query: queryInventory,
  }),
});

export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext: (
    ctx: CreateAWSLambdaContextOptions<APIGatewayProxyEvent>,
  ) => ctx,
  responseMeta: () => ({
    headers: {
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Methods': '*',
    },
  }),
});

export type AppRouter = typeof appRouter;

Task 2: Create an Inventory MCP server

Let us create an MCP server which will allow our agent to manage items in a player’s inventory.

We’ll define the following tools for our agent:

• list-inventory-items for retrieving the player’s current inventory items
• add-to-inventory for adding items to the player’s inventory
• remove-from-inventory for removing items from the player’s inventory

To save time, we will define all the tools inline:

packages/inventory/src/mcp-server/server.ts

+

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import z from 'zod-v3';
import { createInventoryEntity } from ':dungeon-adventure/game-api';

/**
 * Create the MCP Server
 */
export const createServer = () => {
  const server = new McpServer({
    name: 'inventory-mcp-server',
    version: '1.0.0',
  });

  const dynamoDb = new DynamoDBClient();
  const inventory = createInventoryEntity(dynamoDb);

  server.tool(
    'list-inventory-items',
    "List items in the player's inventory. Leave cursor blank unless you are requesting subsequent pages",
    {
      playerName: z.string(),
      cursor: z.string().optional(),
    },
    async ({ playerName }) => {
      const results = await inventory.query
        .primary({
          playerName,
        })
        .go();

      return {
        content: [{ type: 'text', text: JSON.stringify(results) }],
      };
    },
  );

  server.tool(
    'add-to-inventory',
    "Add an item to the player's inventory. Quantity defaults to 1 if omitted.",
    {
      playerName: z.string(),
      itemName: z.string(),
      emoji: z.string(),
      quantity: z.number().optional().default(1),
    },
    async ({ playerName, itemName, emoji, quantity = 1 }) => {
      await inventory
        .put({
          playerName,
          itemName,
          quantity,
          emoji,
        })
        .go();

      return {
        content: [
          {
            type: 'text',
            text: `Added ${itemName} (x${quantity}) to inventory`,
          },
        ],
      };
    },
  );

  server.tool(
    'remove-from-inventory',
    "Remove an item from the player's inventory. If quantity is omitted, all items are removed.",
    {
      playerName: z.string(),
      itemName: z.string(),
      quantity: z.number().optional(),
    },
    async ({ playerName, itemName, quantity }) => {
      // If quantity is omitted, remove the entire item
      if (quantity === undefined) {
        try {
          await inventory.delete({ playerName, itemName }).go();
          return {
            content: [
              { type: 'text', text: `${itemName} removed from inventory.` },
            ],
          } as const;
        } catch {
          return {
            content: [
              { type: 'text', text: `${itemName} not found in inventory` },
            ],
          } as const;
        }
      }

      // If quantity is specified, fetch current quantity and update
      const item = await inventory.get({ playerName, itemName }).go();

      if (!item.data) {
        return {
          content: [
            { type: 'text', text: `${itemName} not found in inventory` },
          ],
        } as const;
      }

      const newQuantity = item.data.quantity - quantity;

      if (newQuantity <= 0) {
        await inventory.delete({ playerName, itemName }).go();
        return {
          content: [
            { type: 'text', text: `${itemName} removed from inventory.` },
          ],
        } as const;
      }

      await inventory
        .put({
          playerName,
          itemName,
          quantity: newQuantity,
          emoji: item.data.emoji,
        })
        .go();

      return {
        content: [
          {
            type: 'text',
            text: `Removed ${itemName} (x${quantity}) from inventory. ${newQuantity} remaining.`,
          },
        ],
      };
    },
  );

  return server;
};

+-

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { registerAddTool } from './tools/add.js';
import { registerSampleGuidanceResource } from './resources/sample-guidance.js';
import z from 'zod-v3';
import { createInventoryEntity } from ':dungeon-adventure/game-api';

/**
 * Create the MCP Server
 */
export const createServer = () => {
  const server = new McpServer({
    name: 'inventory-mcp-server',
    version: '1.0.0',
  });

  registerAddTool(server);
  registerSampleGuidanceResource(server);
  const dynamoDb = new DynamoDBClient();
  const inventory = createInventoryEntity(dynamoDb);

  server.tool(
    'list-inventory-items',
    "List items in the player's inventory. Leave cursor blank unless you are requesting subsequent pages",
    {
      playerName: z.string(),
      cursor: z.string().optional(),
    },
    async ({ playerName }) => {
      const results = await inventory.query
        .primary({
          playerName,
        })
        .go();

      return {
        content: [{ type: 'text', text: JSON.stringify(results) }],
      };
    },
  );

  server.tool(
    'add-to-inventory',
    "Add an item to the player's inventory. Quantity defaults to 1 if omitted.",
    {
      playerName: z.string(),
      itemName: z.string(),
      emoji: z.string(),
      quantity: z.number().optional().default(1),
    },
    async ({ playerName, itemName, emoji, quantity = 1 }) => {
      await inventory
        .put({
          playerName,
          itemName,
          quantity,
          emoji,
        })
        .go();

      return {
        content: [
          {
            type: 'text',
            text: `Added ${itemName} (x${quantity}) to inventory`,
          },
        ],
      };
    },
  );

  server.tool(
    'remove-from-inventory',
    "Remove an item from the player's inventory. If quantity is omitted, all items are removed.",
    {
      playerName: z.string(),
      itemName: z.string(),
      quantity: z.number().optional(),
    },
    async ({ playerName, itemName, quantity }) => {
      // If quantity is omitted, remove the entire item
      if (quantity === undefined) {
        try {
          await inventory.delete({ playerName, itemName }).go();
          return {
            content: [
              { type: 'text', text: `${itemName} removed from inventory.` },
            ],
          } as const;
        } catch {
          return {
            content: [
              { type: 'text', text: `${itemName} not found in inventory` },
            ],
          } as const;
        }
      }

      // If quantity is specified, fetch current quantity and update
      const item = await inventory.get({ playerName, itemName }).go();

      if (!item.data) {
        return {
          content: [
            { type: 'text', text: `${itemName} not found in inventory` },
          ],
        } as const;
      }

      const newQuantity = item.data.quantity - quantity;

      if (newQuantity <= 0) {
        await inventory.delete({ playerName, itemName }).go();
        return {
          content: [
            { type: 'text', text: `${itemName} removed from inventory.` },
          ],
        } as const;
      }

      await inventory
        .put({
          playerName,
          itemName,
          quantity: newQuantity,
          emoji: item.data.emoji,
        })
        .go();

      return {
        content: [
          {
            type: 'text',
            text: `Removed ${itemName} (x${quantity}) from inventory. ${newQuantity} remaining.`,
          },
        ],
      };
    },
  );

  return server;
};

As the number of tools grow, you can refactor them out into separate files if you like.

Delete the tools and resources directories in packages/inventory/src/mcp-server as these will not be used.

Task 3: Update the infrastructure

The final step is to update our infrastructure to create the DynamoDB table and grant permissions to perform operations from the Game API. To do so, update the packages/infra/src as follows:

constructs/electrodb-table.ts

import { CfnOutput } from 'aws-cdk-lib';
import {
  AttributeType,
  BillingMode,
  ProjectionType,
  Table,
  TableProps,
} from 'aws-cdk-lib/aws-dynamodb';
import { Construct } from 'constructs';
import { suppressRules } from ':dungeon-adventure/common-constructs';

export type ElectrodbDynamoTableProps = Omit<
  TableProps,
  'partitionKey' | 'sortKey' | 'billingMode'
>;

export class ElectrodbDynamoTable extends Table {
  constructor(scope: Construct, id: string, props?: ElectrodbDynamoTableProps) {
    super(scope, id, {
      partitionKey: {
        name: 'pk',
        type: AttributeType.STRING,
      },
      sortKey: {
        name: 'sk',
        type: AttributeType.STRING,
      },
      billingMode: BillingMode.PAY_PER_REQUEST,
      ...props,
    });

    this.addGlobalSecondaryIndex({
      indexName: 'gsi1pk-gsi1sk-index',
      partitionKey: {
        name: 'gsi1pk',
        type: AttributeType.STRING,
      },
      sortKey: {
        name: 'gsi1sk',
        type: AttributeType.STRING,
      },
      projectionType: ProjectionType.ALL,
    });

    // Suppress checkov rules that expect a KMS customer managed key and backup to be enabled
    suppressRules(this, ['CKV_AWS_119', 'CKV_AWS_28'], 'No need for custom encryption or backup');

    new CfnOutput(this, 'TableName', { value: this.tableName });
  }
}

stacks/application-stack.ts

+

import {
  GameApi,
  GameUI,
  InventoryMcpServer,
  RuntimeConfig,
  StoryAgent,
  UserIdentity,
} from ':dungeon-adventure/common-constructs';
import { Stack, StackProps, CfnOutput } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { ElectrodbDynamoTable } from '../constructs/electrodb-table.js';

export class ApplicationStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    const userIdentity = new UserIdentity(this, 'UserIdentity');

    const electroDbTable = new ElectrodbDynamoTable(this, 'ElectroDbTable');

    const gameApi = new GameApi(this, 'GameApi', {
      integrations: GameApi.defaultIntegrations(this)
        .withDefaultOptions({
          environment: {
            TABLE_NAME: electroDbTable.tableName,
          },
        })
        .build(),
    });

    electroDbTable.grantReadData(gameApi.integrations['actions.query'].handler);
    electroDbTable.grantReadData(gameApi.integrations['games.query'].handler);
    electroDbTable.grantReadData(gameApi.integrations['inventory.query'].handler);
    electroDbTable.grantReadWriteData(
      gameApi.integrations['actions.save'].handler,
    );
    electroDbTable.grantReadWriteData(
      gameApi.integrations['games.save'].handler,
    );

    const { userPool, userPoolClient } = userIdentity;

    const mcpServer = new InventoryMcpServer(this, 'InventoryMcpServer', {
      environment: {
        TABLE_NAME: electroDbTable.tableName,
      },
    });
    electroDbTable.grantReadWriteData(mcpServer.agentCoreRuntime);

    // Use Cognito for user authentication with the agent
    const storyAgent = new StoryAgent(this, 'StoryAgent', {
      authorizerConfiguration: {
        customJwtAuthorizer: {
          discoveryUrl: `https://cognito-idp.${Stack.of(userPool).region}.amazonaws.com/${userPool.userPoolId}/.well-known/openid-configuration`,
          allowedAudience: [userPoolClient.userPoolClientId],
        },
      },
      environment: {
        INVENTORY_MCP_ARN: mcpServer.agentCoreRuntime.arn,
      },
    });
    // Add the Story Agent ARN to runtime-config.json so it can be referenced by the website
    RuntimeConfig.ensure(this).config.agentArn =
      storyAgent.agentCoreRuntime.arn;

    new CfnOutput(this, 'StoryAgentArn', {
      value: storyAgent.agentCoreRuntime.arn,
    });
    new CfnOutput(this, 'InventoryMcpArn', {
      value: mcpServer.agentCoreRuntime.arn,
    });

    // Grant the agent permissions to invoke our mcp server
    mcpServer.agentCoreRuntime.grantInvoke(storyAgent.agentCoreRuntime);

    // Grant the authenticated role access to invoke the api
    gameApi.grantInvokeAccess(userIdentity.identityPool.authenticatedRole);

    // Ensure this is instantiated last so our runtime-config.json can be automatically configured
    new GameUI(this, 'GameUI');
  }
}

+-

import {
  GameApi,
  GameUI,
  InventoryMcpServer,
  RuntimeConfig,
  StoryAgent,
  UserIdentity,
} from ':dungeon-adventure/common-constructs';
import { Stack, StackProps, CfnOutput } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { ElectrodbDynamoTable } from '../constructs/electrodb-table.js';

export class ApplicationStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    const userIdentity = new UserIdentity(this, 'UserIdentity');

    const electroDbTable = new ElectrodbDynamoTable(this, 'ElectroDbTable');

    const gameApi = new GameApi(this, 'GameApi', {
      integrations: GameApi.defaultIntegrations(this).build(),
      integrations: GameApi.defaultIntegrations(this)
        .withDefaultOptions({
          environment: {
            TABLE_NAME: electroDbTable.tableName,
          },
        })
        .build(),
    });

    electroDbTable.grantReadData(gameApi.integrations['actions.query'].handler);
    electroDbTable.grantReadData(gameApi.integrations['games.query'].handler);
    electroDbTable.grantReadData(gameApi.integrations['inventory.query'].handler);
    electroDbTable.grantReadWriteData(
      gameApi.integrations['actions.save'].handler,
    );
    electroDbTable.grantReadWriteData(
      gameApi.integrations['games.save'].handler,
    );

    const { userPool, userPoolClient } = userIdentity;

    const mcpServer = new InventoryMcpServer(this, 'InventoryMcpServer');
    const mcpServer = new InventoryMcpServer(this, 'InventoryMcpServer', {
      environment: {
        TABLE_NAME: electroDbTable.tableName,
      },
    });
    electroDbTable.grantReadWriteData(mcpServer.agentCoreRuntime);

    // Use Cognito for user authentication with the agent
    const storyAgent = new StoryAgent(this, 'StoryAgent', {
      authorizerConfiguration: {
        customJwtAuthorizer: {
          discoveryUrl: `https://cognito-idp.${Stack.of(userPool).region}.amazonaws.com/${userPool.userPoolId}/.well-known/openid-configuration`,
          allowedAudience: [userPoolClient.userPoolClientId],
        },
      },
      environment: {
        INVENTORY_MCP_ARN: mcpServer.agentCoreRuntime.arn,
      },
    });
    // Add the Story Agent ARN to runtime-config.json so it can be referenced by the website
    RuntimeConfig.ensure(this).config.agentArn =
      storyAgent.agentCoreRuntime.arn;

    new CfnOutput(this, 'StoryAgentArn', {
      value: storyAgent.agentCoreRuntime.arn,
    });
    new CfnOutput(this, 'InventoryMcpArn', {
      value: mcpServer.agentCoreRuntime.arn,
    });

    // Grant the agent permissions to invoke our mcp server
    mcpServer.agentCoreRuntime.grantInvoke(storyAgent.agentCoreRuntime);

    // Grant the authenticated role access to invoke the api
    gameApi.grantInvokeAccess(userIdentity.identityPool.authenticatedRole);

    // Ensure this is instantiated last so our runtime-config.json can be automatically configured
    new GameUI(this, 'GameUI');
  }
}

Note

Notice here that since each procedure is served by an individual lambda function, we can follow the principle of least privilege and assign only the required read/write permissions based on the procedure’s implementation.

Task 4: Deployment and testing

To build the codebase:

pnpm

pnpm nx run-many --target build --all

yarn

yarn nx run-many --target build --all

npm

npx nx run-many --target build --all

bun

bunx nx run-many --target build --all

Tip

If you encounter any lint errors, run the following command to automatically fix them.

pnpm

pnpm nx run-many --target lint --configuration=fix --all

yarn

yarn nx run-many --target lint --configuration=fix --all

npm

npx nx run-many --target lint --configuration=fix --all

bun

bunx nx run-many --target lint --configuration=fix --all

Deploy your application

To deploy your application, run the following command:

pnpm

pnpm nx deploy infra dungeon-adventure-infra-sandbox/*

yarn

yarn nx deploy infra dungeon-adventure-infra-sandbox/*

npm

npx nx deploy infra dungeon-adventure-infra-sandbox/*

bun

bunx nx deploy infra dungeon-adventure-infra-sandbox/*

Caution

To bootstrap your AWS Account first, run:

pnpm

pnpm nx bootstrap infra

yarn

yarn nx bootstrap infra

npm

npx nx bootstrap infra

bun

bunx nx bootstrap infra

Your first deployment will take around 8 minutes to complete. Subsequent deployments will take around 2 minutes.

Tip

If you’re iterating on Lambda function code changes, you can deploy with the --hotswap flag after building the codebase for a much shorter (2-3 second) deployment time.

pnpm

pnpm nx run @dungeon-adventure/infra:deploy dungeon-adventure-infra-sandbox/* --hotswap

yarn

yarn nx run @dungeon-adventure/infra:deploy dungeon-adventure-infra-sandbox/* --hotswap

npm

npx nx run @dungeon-adventure/infra:deploy dungeon-adventure-infra-sandbox/* --hotswap

bun

bunx nx run @dungeon-adventure/infra:deploy dungeon-adventure-infra-sandbox/* --hotswap

Once the deployment completes, you will see outputs similar to the following (some values have been redacted):

dungeon-adventure-sandbox-Application
dungeon-adventure-sandbox-Application: deploying... [2/2]

 ✅  dungeon-adventure-sandbox-Application

✨  Deployment time: 354s

Outputs:
dungeon-adventure-sandbox-Application.ElectroDbTableTableNameXXX = dungeon-adventure-sandbox-Application-ElectroDbTableXXX-YYY
dungeon-adventure-sandbox-Application.GameApiEndpointXXX = https://xxx.execute-api.region.amazonaws.com/prod/
dungeon-adventure-sandbox-Application.GameUIDistributionDomainNameXXX = xxx.cloudfront.net
dungeon-adventure-sandbox-Application.StoryApiEndpointXXX = https://xxx.execute-api.region.amazonaws.com/prod/
dungeon-adventure-sandbox-Application.UserIdentityUserIdentityIdentityPoolIdXXX = region:xxx
dungeon-adventure-sandbox-Application.UserIdentityUserIdentityUserPoolIdXXX = region_xxx

Test the API

You can test the API by either:

• Starting a local instance of the tRPC backend and invoke the APIs using curl.
• Calling the deployed API using sigv4 enabled curl

Local

To start your local game-api server, run the following command:

pnpm

TABLE_NAME=dungeon-adventure-infra-sandbox-Application-ElectroDbTableXXX-YYY pnpm nx run @dungeon-adventure/game-api:serve

yarn

TABLE_NAME=dungeon-adventure-infra-sandbox-Application-ElectroDbTableXXX-YYY yarn nx run @dungeon-adventure/game-api:serve

npm

TABLE_NAME=dungeon-adventure-infra-sandbox-Application-ElectroDbTableXXX-YYY npx nx run @dungeon-adventure/game-api:serve

bun

TABLE_NAME=dungeon-adventure-infra-sandbox-Application-ElectroDbTableXXX-YYY bunx nx run @dungeon-adventure/game-api:serve

Caution

Use the CDK deploy output value of dungeon-adventure-infra-sandbox-Application.ElectroDbTableTableNameXXX to replace the highlighted placeholder.

Once your server is up and running, you can call it by running the following command:

curl -X GET 'http://localhost:2022/games.query?input=%7B%7D'

Deployed

acurl ap-southeast-2 execute-api -X GET 'https://xxx.execute-api.ap-southeast-2.amazonaws.com/prod/games.query?input=%7B%7D'

Caution

Use the CDK deploy output value of dungeon-adventure-infra-sandbox-Application.GameApiGameApiEndpointXXX to replace the highlighted placeholder and set the region accordingly.

Note

The %7B%7D we pass to test the API is a URI encoded empty JSON object ({}).

If the command runs successfully, you will see a response as follows:

{"result":{"data":{"items":[],"cursor":null}}}

Congratulations, you have built and deployed your first API using tRPC! 🎉🎉🎉