# Validator

## Definition
In the Hierarchy multi-agent pattern, the Validator is a checkpoint that checks worker outputs and either accepts them or sends them back for revision. It can be deterministic code (unit tests, JSON schema validation) or an LLM.

## Role in Multi-Agent Hierarchy
- Validates output of each Worker individually or after aggregation
- Uses deterministic code or LLM to verify correctness
- Forces revision if work is substandard
- Prevents cheating by Workers (caught by verification)

## Key Properties
- Best used as a different model than Planner for objectivity
- Two modes: individual Worker validation or aggregated result validation
- Critical component that makes the dependency graph work — Workers can't skip steps

## Related Concepts
- [[Multi-Agent Hierarchy]]
- [[Planner]]
- [[Worker]]