Agents & MCP
Tool call
A single action an agent takes to use an external capability — query a database, search the web, run a function — as opposed to just generating text. Each tool call is a step where the agent reaches outside the model.
Example
To answer "what did we bill Acme last quarter?" the agent makes a tool call to your invoicing system, gets the number back, and folds it into its reply. That one tool call is a governable, recordable event — who called what, when, and why.
Related terms
AI agent
An AI system that doesn't just answer once but works toward a goal over multiple steps — planning, calling tools, reacting to results, and looping until done. Because an agent can make many calls per task, it can spend far more than a single prompt, and it spends without a human watching each step.
MCP (Model Context Protocol)
An open standard for how AI agents connect to external tools and data sources in a consistent way — a common "plug" so any compatible agent can use any compatible tool. It's how modern agents reach beyond the model to your systems.
Audit trail
The connected, time-ordered record of who did what, when, and under what authorization — the evidence you produce when someone asks "what happened?" For AI spend, a good audit trail records intent (the budget authorized) alongside execution (what actually ran).