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Pydantic AI Shields

Guardrail Capabilities for Pydantic AI Agents

PyPI Python License

Pydantic AI Shields provides ready-to-use guardrail capabilities for Pydantic AI agents. Drop them into any agent for cost control, tool permissions, content safety, and more.

Quick Start

Python
from pydantic_ai import Agent
from pydantic_ai_shields import (
    CostTracking, PromptInjection, PiiDetector, SecretRedaction,
)

agent = Agent(
    "openai:gpt-4.1",
    capabilities=[
        CostTracking(budget_usd=5.0),
        PromptInjection(sensitivity="high"),
        PiiDetector(),
        SecretRedaction(),
    ],
)

Available Shields

Infrastructure Shields

Shield Description
CostTracking Token/USD tracking with budget enforcement
ToolGuard Block tools or require human approval
InputGuard Custom input validation (pluggable function)
OutputGuard Custom output validation (pluggable function)
AsyncGuardrail Run guard concurrently with LLM call

Content Shields

Shield Description
PromptInjection Detect prompt injection / jailbreak (6 categories, 3 sensitivity levels)
PiiDetector Detect PII — email, phone, SSN, credit card, IP
SecretRedaction Block API keys, tokens, credentials in output
BlockedKeywords Block forbidden keywords/phrases
NoRefusals Block LLM refusals ("I cannot help with that")

Next Steps