How to Build Programmatic Prerequisites in Claude Code

As I began poring over the study guide recently published by Anthropic for their new Claude Certified Architect exam, I ran into some terms that I had not seen before in the official Claude Code documentation. One of the terms that stood out to me is programmatic prerequisite.

TLDR: it's a term for a hook. And today I'm going to take you through a Claude Code tutorial on programmatic prerequisites so that you too will become familiar with phrase.

If you've read my article on Claude Code Hooks, you already know the principles behind setting up a hook.

A programmatic prerequisite is a way to ensure something happens before something else is allowed to happen. In the sample question found in Anthropic's study guide for the architect exam, the problem was that the wrong customer's order information was sometimes being looked up via the lookup_order function because a call to the get_customer function was being skipped, and order information was being retrieved with a customer name instead. How many people are named John Smith? You can see why looking up orders by a customer name can return the wrong results.

The solution is to set up a programmatic prerequisite that prevents the lookup_order function from being called until a valid customer ID has been returned from the get_customer function.

But what kind of hook would this be? In this case, a PreToolUse hook could be used to block any attempt to call the lookup_order function until a valid Customer ID has been returned from the get_customer function.

What are some ways in your projects that a PreToolUse hook could be useful?

Preparing for the CCA exam? Start with our overview: What Is Anthropic's Claude Certified Architect Exam?