AI has no window
You ask AI whether it will rain in Da Lat tomorrow, and it answers right away, with the temperature too. But AI has no window and no phone. So where did that come from?
THE SECRET
AI can only write
The secret: AI doesn't press any buttons itself. It can only write text. So when it needs outside information, it writes a request slip, called a tool call.
REQUEST SLIP
The slip makes a round trip
The slip says: use the weather tool, place Da Lat, tomorrow. The app reads the slip, asks a weather service, then hands the result back to AI.
TOOL CALLING
Only then does it answer
With the result in hand, AI writes its answer to you. That whole loop is called tool calling: AI calling a tool.
THE LIST
A tool board on the wall
Each tool is one line of description: its name, what it does, what information it needs. AI reads that list to know when to use which one. Web search, checking a calendar, doing math: they all work this way.
DOES AI DECIDE?
The app holds the power
Because AI only writes slips, the power to act stays with the app. If a slip asks to send email or pay money, a good app stops and asks you first.
NEXT
A hundred kinds of slips
But every app uses its own kind of slip. To connect AI to a hundred tools, do you have to build it a hundred times? Part two: a shared port called MCP.
This article is based on the video Tool calling: how AI uses tools from the Mark học AI channel. Watch the video (in Vietnamese) to see the animations.