Day 3: What are Tools?

Welcome to Day 3 of Building Agentic AI Applications!

Note: Apologies for the delay, the email automation app I was using flagged my account (we’ve got over 10,000 people taking the course, and I guess they thought that was suspicious... sigh). I’m switching to Substack starting today. The course will still be free, and you’ll also find older posts at the link below.

Missed previous days’ posts? Find them here

Yesterday, we talked about different types of agents, from rule-based to fully autonomous, and how the right level of autonomy depends on the problem you're solving.

But here's a shared trait across all agent types, no matter how simple or complex:

They rely on tools to perform actions.

So what are tools anyway?

What Are “Tools” in AI?

In the context of agentic AI, tools are external capabilities the LLM can invoke, things like:

• APIs

• Database queries

• Internal services

• Third-party systems

• Internal func…