What Are Guardrails?
Guardrails act as protective middleware layers that intercept and validate LLM inputs and outputs in real-time. They enable you to:- Prevent harmful outputs - Block inappropriate, biased, or unsafe content before it reaches users
- Enforce business policies - Ensure responses comply with company guidelines and regulatory requirements
- Validate quality - Check for hallucinations, factual accuracy, and relevance in real-time
- Control behavior - Enforce tone, style, and format requirements consistently
- Protect sensitive data - Detect and prevent leakage of PII, credentials, or confidential information
How Guardrails Differ from Other Evaluators
| Feature | Guardrails | Experiments | Monitors | Playgrounds |
|---|---|---|---|---|
| Timing | Real-time (inline) | Post-hoc (batch) | Post-hoc (continuous) | Interactive (manual) |
| Execution | Synchronous with code | Programmatic via SDK | Automated on production data | User-triggered |
| Purpose | Prevention & blocking | Systematic testing | Quality tracking | Development & testing |
| Latency Impact | Yes - adds to response time | No | No | N/A |
| Can Block Output | Yes | No | No | No |
Use Cases
Safety and Content Filtering
Prevent toxic, harmful, or inappropriate content from reaching users:- Detect hate speech, profanity, or offensive language
- Block outputs containing violent or explicit content
- Filter responses that could cause psychological harm
Regulatory Compliance
Ensure outputs meet legal and regulatory requirements:- HIPAA compliance for medical information
- GDPR compliance for personal data handling
- Financial services regulations (e.g., avoiding financial advice)
- Industry-specific content guidelines
Data Protection
Prevent sensitive information leakage:- Detect PII (personally identifiable information)
- Block API keys, passwords, or credentials in responses
- Prevent disclosure of proprietary business information
- Ensure customer data confidentiality
Quality Assurance
Maintain output quality standards:- Detect hallucinations and factual errors
- Verify response relevance to user queries
- Enforce minimum quality thresholds
- Validate structured output formats
Brand and Tone Control
Ensure consistent brand voice:- Enforce communication style guidelines
- Maintain appropriate tone for audience
- Prevent off-brand language or messaging
- Control formality levels
Implementation
Basic Setup
First, initialize the Traceloop SDK in your application:Using the @guardrail Decorator
Apply the@guardrail decorator to functions that interact with LLMs:
slug parameter identifies which guardrail evaluator to apply. This corresponds to an evaluator you’ve defined in the Traceloop dashboard.
Medical Chat Example
Here’s a complete example showing guardrails for a medical chatbot:Multiple Guardrails
You can apply multiple guardrails to the same function for layered protection:Creating Guardrail Evaluators
Guardrails use the same evaluator system as experiments and monitors. To create a guardrail evaluator:- Navigate to the Evaluator Library in your Traceloop dashboard
- Click New Evaluator or select a pre-built evaluator
-
Define your evaluation criteria:
- For safety checks: Specify content categories to detect and block
- For compliance: Define regulatory requirements and policies
- For quality: Set thresholds for relevance, accuracy, or completeness
- Test the evaluator in a playground to validate behavior
- Note the evaluator’s slug for use in your code
-
Apply the evaluator using
@guardrail(slug="your-evaluator-slug")
Best Practices
Performance Considerations
Guardrails add latency to your application since they run synchronously:- Use selectively - Apply guardrails only where needed, not to every function
- Choose efficient evaluators - Simpler checks run faster than complex LLM-based evaluations
- Consider async execution - Use async/await patterns to maximize throughput
- Monitor latency - Track guardrail execution times and optimize slow evaluators
- Cache when possible - Cache evaluation results for identical inputs
Error Handling
Implement robust error handling for guardrail failures:Layered Protection
Use multiple layers of guardrails for critical applications:- Input validation - Check user inputs before processing
- Output validation - Verify LLM responses before returning
- Context validation - Ensure proper use of retrieved information
- Post-processing - Final safety check on formatted outputs
Testing Guardrails
Before deploying to production:- Test in playgrounds - Validate evaluator behavior with sample inputs
- Run experiments - Test guardrails against diverse datasets
- Monitor false positives - Track blocked outputs that should have been allowed
- Monitor false negatives - Watch for policy violations that weren’t caught
- A/B test - Compare user experience with and without specific guardrails
Compliance and Auditing
For regulated industries:- Log all evaluations - Traceloop automatically tracks all guardrail executions
- Document policies - Maintain clear documentation of what each guardrail checks
- Version control - Track changes to guardrail configurations over time
- Regular audits - Review guardrail effectiveness and update as needed
- Incident response - Have procedures for when guardrails detect violations
Configuration Options
When applying guardrails, you can configure behavior:Monitoring Guardrail Performance
Track guardrail effectiveness in your Traceloop dashboard:- Execution frequency - How often each guardrail runs
- Block rate - Percentage of requests blocked by guardrails
- Latency impact - Time added by guardrail evaluation
- Error rate - Guardrail failures or timeouts
- Policy violations - Trends in detected issues over time
Integration with Experiments and Monitors
Guardrails complement other evaluation workflows:- Experiments - Test guardrail effectiveness on historical data before deployment
- Monitors - Continuously track guardrail performance in production
- Playgrounds - Develop and refine guardrail evaluators interactively
Next Steps
- Create custom evaluators for your specific guardrail needs
- Explore pre-built evaluators for common safety and quality checks
- Set up experiments to test guardrails before production
- Configure monitors to track guardrail performance over time

