Advanced~28 minHazelJS
Guardrails and Tool I/O Hygiene
Import GuardrailsModule with AgentModule; redact PII and block injection on tool I/O—with config sketch.
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Direct answer
GuardrailsModule + AgentModule enables automatic tool I/O checks. Configure redactPIIByDefault, blockInjectionByDefault, and blocklists. Guardrails complement Skillgate curation and PolicyEngine—they do not replace allow-lists.
Docs: Guardrails. Guide: /guides/secure-mcp-servers-and-agent-tools.
Worked example — module wiring
typescript
import { Module } from '@hazeljs/core';
import { AgentModule } from '@hazeljs/agent';
import { GuardrailsModule } from '@hazeljs/guardrails';
@Module({
imports: [
GuardrailsModule.forRoot({
redactPIIByDefault: true,
blockInjectionByDefault: true,
// injectionBlocklist / toxicityBlocklist per package docs
}),
AgentModule.forRoot({ /* agents, llmProvider, ... */ }),
],
})
export class AppModule {}
Still curate tools:
typescript
const gate = Skillgate.fromOpenApi(spec, { include: { tags: ['agent'] } });
gate.register(registry, 'api-concierge');
Artifact: Guardrails config snippet reviewed by security