Building a Self-Correcting Python Agent with Claude's Tool Use

Most Claude agent tutorials show the happy path: model calls a tool, tool returns a result, model uses it. That's fine for demos. Production is messier. In production, tools fail. The API you're calling is down. The file doesn't exist. The regex didn't match. What does your agent do then? Bad answer: crash with an unhandled exception. Worse answer: the model silently ignores the error and hallucinates a response. Better answer: the agent detects the failure and tries something different. Here's how to build that. The Basic Agent Loop First, the minimal scaffolding. We're using the anthropic Python library with tool use: import anthropic import json client = anthropic . Anthropic () def run_agent ( user_task : str , tools : list , tool_handler ) -> str : messages = [{ " role " : " user " , " content " : user_task }] while True : response = client . messages . create ( model = " claude-sonnet-4-5 " , max_tokens = 1024 , tools = tools , messages = messages ) if response . stop_reason == "