Guardrails Overview - Agency Swarm

Guardrails are checkpoint functions that keep agent behavior safe and predictable. Use them to validate incoming messages before execution and validate responses before delivery.

Choose the Right Guardrail

Type	Runs When	On Failure	Page
Input Guardrails	Before the agent processes input	Return guidance (non-strict) or raise `InputGuardrailTripwireTriggered` (strict)	Input Guardrails
Output Guardrails	After the agent drafts output, before delivery	Retry up to `validation_attempts`, then raise `OutputGuardrailTripwireTriggered`	Output Guardrails

Runnable GitHub Examples

Input guardrails example: examples/guardrails_input.py
Output guardrails example: examples/guardrails_output.py

Best Practices

Keep each guardrail focused on one responsibility.
Write clear output_info messages so the model knows how to recover.
Use non-strict mode for guidance and strict mode for hard requirements.
For tool argument validation (field/model validators), use Input Validation.

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