---
term: "Tool use"
category: "Agents and autonomy"
url: https://agenticopenfinance.com/glossary/tool-use
source: AgenticOpenFinance glossary
---

# Tool use

> A model asking its host application to run a named function with structured arguments, then receiving the result.

Tool use, also called function calling, is the pattern in which a model asks the host application to run a named function with structured arguments, such as looking up a balance or drafting a payment, and then receives the result. The Model Context Protocol standardises how servers expose tools, each with a name, a description and an input schema. The model only proposes the call; the host decides whether to run it, which is where consent, limits and logging belong.

Related terms: [Model Context Protocol (MCP)](https://agenticopenfinance.com/glossary/model-context-protocol.md), [MCP server](https://agenticopenfinance.com/glossary/mcp-server.md), [AI agent](https://agenticopenfinance.com/glossary/ai-agent.md), [Excessive agency](https://agenticopenfinance.com/glossary/excessive-agency.md)