Source: https://uptimeify.io/resources/platform-and-support/glossary/tool-call

# Tool Call

> A tool call is a model's structured request to run exactly one named function with validated arguments. Execution happens outside the model.

The model does not run code. It emits a call such as `check_ssl` with `{"host": "deinkunde.com"}`, the client passes it to the [MCP server](/resources/platform-and-support/glossary/mcp-server), and the result comes back into context as a tool result. Only then does the model read the certificate data. That split is the whole point: reasoning stays probabilistic, execution stays deterministic and auditable. Every call can be logged, rate limited or refused before it touches a production system.