Core difference
| Tool | Primary job | Best at |
|---|---|---|
| Guardrails | Output structure and policy rules | JSON schemas, validators, formatting constraints |
| QWED | Deterministic verification | Math, logic, code, SQL, tool-call verification |
When Guardrails is enough
Use Guardrails when you need:- Valid JSON or XML
- Required fields and schema checks
- Basic policy filters
- Controlled output formats for downstream parsing
When you need QWED
Use QWED when you need:- Formal verification for LLM outputs
- AI agent security before tool execution
- Verified tool calls and MCP security
- Deterministic checks for numbers, logic, code, and SQL
Best-practice stack
Use both together:- Guardrails enforces the response format.
- QWED verifies whether the contents are actually correct.