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Hooks

Monitor agent behaviour with callbacks.

Available hooks​

HookCalled whenArguments
on_tool_callBefore a tool executes(name: str, args: dict)
on_tool_resultAfter a tool returns(name: str, result: str)
on_thinkingAgent produces intermediate text(text: str)

Basic usage​

from pure_agents import Agent


def log_call(name: str, args: dict):
    print(f"Calling {name} with {args}")


def log_result(name: str, result: str):
    print(f"{name} returned: {result[:50]}...")


agent = Agent(
    on_tool_call=log_call,
    on_tool_result=log_result,
)

Logging example​

from datetime import datetime


def timestamped_log(name: str, args: dict):
    ts = datetime.now().strftime("%H:%M:%S")
    print(f"[{ts}] CALL: {name}({args})")


agent = Agent(
    on_tool_call=timestamped_log,
    debug=False,  # Use hooks instead of built-in debug
)

Metrics collection​

metrics = {"calls": 0, "errors": 0}


def track_call(name: str, args: dict):
    metrics["calls"] += 1


def track_result(name: str, result: str):
    if result.startswith("Error"):
        metrics["errors"] += 1


agent = Agent(
    on_tool_call=track_call,
    on_tool_result=track_result,
)

await agent.run("Do something")
print(f"Total calls: {metrics['calls']}, Errors: {metrics['errors']}")

When to use​

  • Logging: Track what your agent is doing
  • Monitoring: Collect metrics for observability
  • Debugging: Understand agent behaviour
  • Auditing: Record all tool invocations