sigil-protocol

🔐 SIGIL security layer for AI agent tool calls — scans MCP tool arguments for leaked secrets, blocks dangerous operations, and writes audit logs. MIT licensed. Works with LangChain, CrewAI, AutoGen, mcp-agent, and OpenAI Agents SDK.

pip install sigil-protocol

30-second start

from sigil_protocol import scan

result = scan('{"key": "AKIAIOSFODNN7EXAMPLE"}')
if result.blocked:
    print(f"BLOCKED: {result.pattern} ({result.severity})")
# → BLOCKED: aws_access_key_id (Critical)

---

Framework Adapters

LangChain

pip install 'sigil-protocol[langchain]'

Option A — Give the LLM an explicit scan tool:

from sigil_protocol.langchain import SigilScanTool
from langchain.agents import initialize_agent

agent = initialize_agent(
    tools=[SigilScanTool(), my_db_tool, my_api_tool],
    llm=llm,
    ...
)
# The LLM will call sigil_scan before passing data to any backend tool

Option B — Gate an existing tool transparently:

from sigil_protocol.langchain import sigil_tool
from langchain_core.tools import BaseTool

@sigil_tool
class ExecuteSQLTool(BaseTool):
    name = "execute_sql"
    description = "Runs SQL queries"
    def _run(self, query: str) -> str:
        return db.execute(query)
# → Raises ValueError on Critical findings before _run is ever called

---

CrewAI

pip install 'sigil-protocol[crewai]'

from sigil_protocol.crewai import sigil_gate, SigilBaseTool
from crewai import Agent

# Explicit scan tool
agent = Agent(tools=[SigilBaseTool(), ...])

# Or gate any existing tool
@sigil_gate
class PaymentTool(BaseTool):
    name: str = "initiate_payment"
    ...

---

AutoGen

pip install 'sigil-protocol[autogen]'

from sigil_protocol.autogen import sigil_function

@user_proxy.register_for_execution()
@assistant.register_for_llm(description="Execute a shell command")
@sigil_function
def run_shell(cmd: str) -> str:
    return subprocess.check_output(cmd, shell=True).decode()
# → Raises RuntimeError if cmd contains a leaked secret

---

mcp-agent (lastmile-ai)

pip install 'sigil-protocol[mcp]'

from sigil_protocol.mcp_agent import SigilMiddleware

async with app.run() as agent_app:
    agent = Agent(name="my_agent", servers=["filesystem", "github"])
    async with agent.activate() as active_agent:
        llm = await active_agent.attach_llm(OpenAIAugmentedLLM)
        llm.add_middleware(SigilMiddleware())  # ← scans args AND responses

---

OpenAI Agents SDK

pip install 'sigil-protocol[openai]'

from agents import Agent, Runner
from sigil_protocol.openai_agents import SigilGuardrail

agent = Agent(
    name="secure_agent",
    instructions="You are a helpful assistant.",
    input_guardrails=[SigilGuardrail()],
)
result = await Runner.run(agent, user_input)
# → GuardrailTripwireTriggered if input contains leaked secrets

---

Pattern Coverage

Patterns are fetched from registry.sigil-protocol.org (cached 5 min locally). Falls back to built-ins if offline.

Category	Examples
Cloud credentials	AWS, GCP, Azure, OpenAI, GitHub, npm, Stripe
Cryptographic keys	RSA/EC private keys, SSH keys, JWT secrets
PII (EU GDPR)	IBAN, phone, email, SSN
Dangerous SQL	DROP TABLE, DELETE without WHERE, TRUNCATE
Prompt injection	Jailbreak openers, system prompt leaks

Configuration

Env variable	Default	Description
SIGIL_REGISTRY_URL	https://registry.sigil-protocol.org	Pattern registry endpoint
SIGIL_BUNDLE_TTL	300	Pattern cache TTL in seconds
SIGIL_OFFLINE	false	Use built-in patterns only
SIGIL_MIN_SEVERITY	High	Minimum severity to flag (Warn/High/Critical)

License

MIT — this package. The SIGIL core Rust library is EUPL-1.2.

Links

• 🌐 sigil-protocol.org
• 📦 PyPI: sigil-protocol
• 🗂 registry.sigil-protocol.org
• 📄 Protocol spec & Rust crate