Agent SDK Hooks: Worked Example — Agentic Architecture & Orchestration (Claude Certified Architect)
Agent SDK Hooks: A Worked Example in Agentic Architecture In the Claude Certified Architect - Foundation certification, mastering Agent SDK hooks is...
Agent SDK Hooks: A Worked Example in Agentic Architecture
In the Claude Certified Architect - Foundation certification, mastering Agent SDK hooks is essential for building flexible and robust agentic loops and multi-agent systems. SDK hooks allow developers to intercept and manipulate tool calls programmatically, enabling fine-grained control over task execution and orchestration.
Scenario Overview
Consider a multi-agent system designed to autonomously manage a customer support workflow. The system includes a Coordinator Agent that delegates specific tasks to Subagents such as:
- Information Retrieval Agent
- Response Generation Agent
- Sentiment Analysis Agent
We want to implement an SDK hook to intercept tool calls made by the Response Generation Agent to validate and log the generated responses before they are sent to the customer.
Step 1: Define the Hook Function
The hook function acts as a middleware that intercepts tool calls. It receives the call context and can modify inputs, outputs, or trigger side effects such as logging.
Code Snippet
Define a hook to log and validate response content:
function responseValidationHook(toolCall) { // Extract the response text const responseText = toolCall.inputs.text; // Simple validation: check for prohibited words const prohibitedWords = ['error', 'fail']; const containsProhibited = prohibitedWords.some(word => responseText.includes(word)); if (containsProhibited) { // Modify response or flag for review toolCall.outputs = { text: 'Response flagged for review due to prohibited content.' }; } else { // Log the valid response console.log('Valid response:', responseText); } // Continue with the original or modified output return toolCall; }Step 2: Register the Hook with the Agent SDK
Using the Claude Agent SDK, hooks are registered to intercept specific tool calls. Here, we attach responseValidationHook to the Response Generation Agent's tool calls.
Code Snippet
const responseAgent = new Agent('ResponseGenerationAgent'); // Register the hook responseAgent.registerHook('toolCall', responseValidationHook);Step 3: Implement Multi-Step Workflow with Hook Enforcement
In the orchestrated workflow, when the Response Generation Agent produces an output, the hook intercepts the tool call, validates it, and either allows it to proceed or modifies it accordingly.
Workflow Execution
- The Coordinator Agent sends a query to the Information Retrieval Agent.
- Information Retrieval Agent returns relevant data.
- The Coordinator forwards data to the Response Generation Agent.
- The Response Generation Agent generates a response, triggering the responseValidationHook.
- The hook validates and logs the response or flags it.
- If valid, the Coordinator sends the response to the customer; if flagged, it triggers a review subworkflow.
Step 4: Manage Session State and Context Passing
The hook can also interact with session state to maintain continuity or fork workflows based on validation results.
- If the response is flagged, the hook can spawn a subagent tasked with manual review.
- Context passing ensures the review agent receives the flagged response and relevant metadata.
Summary
This worked example demonstrates how to leverage Agent SDK hooks within the Claude Agent SDK to intercept, validate, and log tool calls in a multi-agent system. By programmatically enforcing validation rules and managing session state, architects can build resilient and autonomous workflows that maintain quality control and enable dynamic task decomposition.
Mastering SDK hooks is a foundational skill for the Claude Certified Architect - Foundation certification, empowering you to design sophisticated agentic loops and orchestrations.
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