Tool use & protocols (MCP)
Letting a model call functions and services through structured requests, standardised by protocols such as MCP.
D1 · StoryFor young children and total beginners
On its own an AI can only talk. Giving it tools is like giving it a phone and a calculator: now it can check the weather or do exact maths.
It asks in a special format, and a program does the actual work.
Like: Handing someone a phone and a calculator.
D2 · PictureFor curious beginners
Developers describe each tool with a name, a description and a schema for its arguments.
When a tool would help, the model outputs a structured tool call instead of prose; the application runs the tool and returns the result to the model.
Protocols such as the Model Context Protocol (MCP) standardise how tools and data sources are offered to AI applications, so one integration works across many clients.
One tool call
- Tool list: names + schemas
- Tool call: structured request
- Execute: by the application
- Result: back into context
- Continue: model answers
Like: Handing someone a phone and a calculator.
Where it breaks: A person decides whether to believe what they hear on the phone. Models tend to treat tool results as trustworthy, so malicious text inside a result can steer them (prompt injection).
D5 · FrontierFor experts
Open problems: securing tool ecosystems against poisoned tools and over-broad permissions, authentication for remote tools, and agents discovering tools on the fly.