---
title: Facts (NeMo Guardrail)
type: guardrail
provider: nvidia
category: safety
source: 'https://github.com/NVIDIA-NeMo/Guardrails'
license: Apache-2.0
tags:
  - guardrail
  - nemo
  - rails
  - colang
dateAdded: '2026-02-15'
featured: false
origin: official
language: en
description: >-
  flow self check facts """Check if the previous answer is accurate w.r.t. the
  relevant chunks. This output rail must be enabled explicitly per output m
---

```coffee
flow self check facts
  """Check if the previous answer is accurate w.r.t. the relevant chunks.

  This output rail must be enabled explicitly per output message by setting
  the $check_facts context variable to True.
  """
  if $check_facts == True
    global $check_facts
    $check_facts = False

    $accuracy = await SelfCheckFactsAction
    if $accuracy < 0.5
      if $system.config.enable_rails_exceptions
        send FactCheckRailException(message="Fact check failed. The accuracy of the previous answer was below the required threshold.")
      else
        bot refuse to respond
      abort
```