Issue #66: Implement Agent Class

examples/first-agent/.gitignore

@@ -0,0 +1,3 @@
+dist
+node_modules
+package-lock.json

examples/first-agent/package.json

@@ -0,0 +1,21 @@
+{
+  "name": "first-agent",
+  "private": true,
+  "main": "dist/index.js",
+  "type": "module",
+  "scripts": {
+    "clean": "rm -rf dist node_modules package-lock.json",
+    "build": "tsc",
+    "start": "tsc && node dist/index.js"
+  },
+  "workspaces": [
+    "../../"
+  ],
+  "dependencies": {
+    "@strands-agents/sdk": "*"
+  },
+  "devDependencies": {
+    "@types/node": "^20.0.0",
+    "typescript": "^5.5.0"
+  }
+}

examples/first-agent/src/index.ts

@@ -0,0 +1,104 @@
+import { type Tool, type ToolResult, type ToolContext, Agent, BedrockModel } from '@strands-agents/sdk'
+
+// Define the shape of the expected input
+type WeatherToolInput = {
+  location: string
+}
+
+// Type Guard: A function that performs a runtime check and informs the TS compiler.
+function isValidInput(input: any): input is WeatherToolInput {
+  return input && typeof input.location === 'string'
+}
+
+class WeatherTool implements Tool {
+  name = 'get_weather'
+  description = 'Get the current weather for a specific location.'
+
+  toolSpec = {
+    name: this.name,
+    description: this.description,
+    inputSchema: {
+      type: 'object' as const,
+      properties: {
+        location: {
+          type: 'string' as const,
+          description: 'The city and state, e.g., San Francisco, CA',
+        },
+      },
+      required: ['location'],
+    },
+  }
+
+  async *stream(context: ToolContext): AsyncGenerator<never, ToolResult, unknown> {
+    const input = context.toolUse.input
+
+    // Use the type guard for validation
+    if (!isValidInput(input)) {
+      throw new Error('Tool input must be an object with a string "location" property.')
+    }
+
+    // After this check, TypeScript knows `input` is `WeatherToolInput`
+    const location = input.location
+
+    console.log(`\n[WeatherTool] Getting weather for ${location}...`)
+
+    const fakeWeatherData = {
+      temperature: '72°F',
+      conditions: 'sunny',
+    }
+
+    const resultText = `The weather in ${location} is ${fakeWeatherData.temperature} and ${fakeWeatherData.conditions}.`
+
+    return {
+      toolUseId: context.toolUse.toolUseId,
+      status: 'success' as const,
+      content: [{ type: 'textBlock', text: resultText }],
+    }
+  }
+}
+
+/**
+ * A helper function to run an agent scenario and handle its output stream.
+ * This avoids repeating the for-await loop and logging logic.
+ * @param title The title of the scenario to be logged.
+ * @param agent The agent instance to use.
+ * @param prompt The user prompt to invoke the agent with.
+ */
+async function run(title: string, agent: Agent, prompt: string) {
+  console.log(`--- ${title} ---`)
+  console.log(`User: ${prompt}`)
+
+  const responseStream = agent.invoke(prompt)
+
+  console.log('Agent response stream:')
+  let result = await responseStream.next()
+  while (!result.done) {
+    const event = result.value
+    console.log('[Event]', event)
+    result = await responseStream.next()
+  }
+
+  // Clean up logging for the next scenario
+  console.log('\nInvocation complete.\n')
+}
+
+async function main() {
+  // 1. Initialize the components
+  const model = new BedrockModel()
+  const weatherTool = new WeatherTool()
+
+  // 2. Create agents
+  const defaultAgent = new Agent()
+  const agentWithoutTools = new Agent({ model })
+  const agentWithTools = new Agent({
+    systemPrompt: 'You are a helpful assistant that provides weather information using the get_weather tool.',
+    model,
+    tools: [weatherTool],
+  })
+
+  await run('0: Invocation with default agent (no model or tools)', defaultAgent, 'Hello!')
+  await run('1: Invocation with a model but no tools', agentWithoutTools, 'Hello!')
+  await run('2: Invocation that uses a tool', agentWithTools, 'What is the weather in Toronto? Use the weather tool.')
+}
+
+main().catch(console.error)

examples/first-agent/tsconfig.json

@@ -0,0 +1,19 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": ["ES2022"],
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist", "tests*"]
+}

package.json

@@ -84,6 +84,8 @@
   "homepage": "https://github.com/strands-agents/sdk-typescript#readme",
   "dependencies": {
     "@aws-sdk/client-bedrock-runtime": "^3.911.0",
+    "@modelcontextprotocol/sdk": "^1.20.2",
+    "uuid": "^13.0.0",
     "zod": "^4.1.12"
   },
   "optionalDependencies": {

src/__fixtures__/tool-helpers.ts

@@ -38,7 +38,7 @@ export function createMockTool(
   resultFn: () => ToolResult | AsyncGenerator<never, ToolResult, never>
 ): Tool {
   return {
-    toolName: name,
+    name,
     description: `Mock tool ${name}`,
     toolSpec: {
       name,