Free AI agent safety tools

You do not need a budget to add safety controls to your AI agent. Several open-source tools provide production-grade safety features at no cost. This guide covers the best free options.

Policy enforcement

Authensor (MIT license)

Full safety stack for AI agents: policy engine, content scanner (Aegis), behavioral monitor (Sentinel), approval workflows, and hash-chained audit trails. TypeScript and Python SDKs. Framework adapters for LangChain, OpenAI, and CrewAI.

pnpm add @authensor/sdk

Zero cost. Self-hosted. No per-request pricing.

Content safety

Aegis (part of Authensor, MIT license)

Prompt injection detection, PII scanning, and credential detection. Zero runtime dependencies. Runs in-process in microseconds.

pnpm add @authensor/aegis

Rebuff (Apache 2.0)

Prompt injection detection using multiple methods: heuristic analysis, LLM-based detection, and vector database similarity matching. Python only.

Conversational guardrails

NeMo Guardrails (Apache 2.0)

Conversational safety for chatbots. Topic control, content filtering, and dialogue management using the Colang language. By NVIDIA.

Output validation

Guardrails AI (Apache 2.0)

LLM output validation against schemas and quality criteria. Rich validator ecosystem. Python only.

Content classification

LlamaGuard (Llama license)

Fine-tuned Llama model for safety classification. High accuracy on harmful content categories. Requires GPU for inference.

Behavioral monitoring

Sentinel (part of Authensor, MIT license)

Real-time behavioral anomaly detection using EWMA and CUSUM statistical analysis. Tracks action rates, denial rates, and tool distribution. Zero dependencies.

Observability

Langfuse (MIT license)

Open-source LLM observability platform. Tracing, prompt management, and cost tracking. Self-hostable.

Getting started for free

The minimum viable safety stack costs nothing:

1. Authensor SDK: Policy enforcement + receipt generation
2. Aegis: Prompt injection detection
3. Sentinel: Behavioral monitoring

All three run in your application process with zero infrastructure requirements. No database, no server, no external API calls. Add the control plane (PostgreSQL) when you need centralized management.

When to consider paid tools

Free tools cover the core safety requirements. Consider paid tools when you need:

• Managed infrastructure (someone else runs it)
• 24/7 vendor support
• Advanced content classification (beyond pattern matching)
• Enterprise SSO and access management
• SLA guarantees

But start free. You can add paid tools later without replacing what you built with open-source tools.