04-tools-agent-loop

04: Tools & Agent Loop

Key Insight: The agent loop turns a chatbot into an agent — call tools until done.

What's New vs 03

• 4 tools: run_command, read_file, write_file, web_search
• The agent loop — keeps calling Claude until it stops requesting tools
• Content serialization for safe session storage
• Tool dispatch pattern

What You'll Learn

• How tool definitions work in the Anthropic API
• The agent loop pattern (the most important pattern in AI agents)
• How to serialize mixed content (text + tool calls) for persistence
• The execute/dispatch pattern for routing tool calls

Tool Table

Tool	Description	Example Use
run_command	Execute a shell command	"List files in the current directory"
read_file	Read file contents	"Show me the contents of bot.py"
write_file	Create/overwrite a file	"Create a hello.py script"
web_search	Search the web (placeholder)	"Search for Python best practices"

Prerequisites

• Completed module 03
• Anthropic API key and Telegram bot token in .env

How to Run

make 04-tools-agent-loop
# or
uv run python 04-tools-agent-loop/bot.py

What to Observe

1. The bot takes actions — Ask it to create a file and it actually does
2. Multiple tool calls — Complex tasks may trigger several tool calls in sequence
3. The loop — Watch the console output to see tool calls being executed

Files

File	Lines	Description
bot.py	~200 lines	Bot with tools and agent loop

Next Module

Ready for safety? -> 05: Permission Controls