---
title: "Tool-calling · agent building block · Agent Fieldbook"
url: https://agentfieldbook.org/design/building_blocks/tool-call/
description: "invokes external tools / APIs"
section: "Design · Building Blocks · Node"
source: Agent Fieldbook — generated from the published page
---

# Tool-calling

invokes external tools / APIs

## What it does

## At a glance

| Field | Value |
| --- | --- |
| Kind | Functional node |
| Example agents | most agents |

## Basis

- [modelcontextprotocol.io](https://modelcontextprotocol.io/specification/)