Why Agents SDK needs a before tool call hook

Agree completely — the model shouldn’t own budget enforcement, that’s the core issue with the tool-based approach I showed.

The guardrail path is cleaner. Something like:

from agents import Agent, Runner, input_guardrail, GuardrailFunctionOutput

@input_guardrail

async def spend_guard(ctx, agent, input):

approved = check_budget(estimated_cost=0.05) # your policy check

return GuardrailFunctionOutput(

output_info={"approved": approved},

tripwire_triggered=not approved,

)

agent = Agent(

name="Research Agent",

input_guardrails=[spend_guard],

tools=[...],

)

The hard outer limit is the right safety net — but guardrails give you per-call granularity before the runner even sees it.

Is there a way to pass per-tool cost estimates into guardrails yet, or does it only have access to the full input at that point?