---
id: "prereq-agent-tool-calling"
type: "prereq"
source_timestamps: ["01:45:00", "06:00:00"]
tags: ["ai-agents"]
related: ["concept-shift-in-callers", "concept-orchestrator-pattern"]
reason: "The entire thesis rests on the premise that LLMs are no longer just chatbots, but agents capable of autonomously invoking external tools (skills) to accomplish multi-step goals."
sources: ["s43-file-format-agreement"]
sourceVaultSlug: "s43-file-format-agreement"
originDay: 43
---
# Understanding of Agent Tool Calling

## Prerequisite

A working understanding of **agent tool calling** — the pattern in which an LLM autonomously selects and invokes external tools (functions, APIs, scripts, or skill files) to accomplish a multi-step goal.

## Why It's Required

The entire thesis of the source rests on the premise that LLMs are no longer just chatbots, but agents capable of autonomously invoking external tools. Without this mental model, [[concept-shift-in-callers]], [[concept-orchestrator-pattern]], and [[concept-specialist-stack]] do not make sense.

## Quick Catch-Up

Key ideas to know:

- Function calling / tool calling APIs (OpenAI, Anthropic).
- The agent loop: plan → call tool → observe result → re-plan.
- Multi-agent orchestration via frameworks (LangChain, CrewAI, AutoGen, LangGraph).
- The role of [[entity-product-mcp]] as a connector standard.