Sigil Notary

Tamper-evident audit trails for AI agents.

Sigil gives AI agents cryptographically signed, hash-chained audit trails via the Model Context Protocol. Every action gets a verifiable receipt with an Ed25519 signature and SHA-256 chain link.

Install

pip install sigil-notary

MCP Server Usage

Sigil ships as an MCP server that any MCP-compatible AI agent can use natively.

Claude Code

Add to your .claude/settings.json or project MCP config:

{
  "mcpServers": {
    "sigil": {
      "command": "uvx",
      "args": ["sigil-notary"],
      "env": {
        "SIGIL_API_KEY": "sg_your_key_here",
        "SIGIL_API_URL": "https://api.sigil-notary.dev"
      }
    }
  }
}

Available MCP Tools

Tool	Description
attest_action	Record an action and get a signed, hash-chained receipt
verify_receipt	Verify a receipt's signature and chain integrity
get_chain	Retrieve the full audit trail for the current agent

Python SDK

For programmatic access, use the Python client directly:

from sigil import SigilClient

client = SigilClient(api_key="sg_your_key_here")

# Record an action
receipt = client.attest(
    action_type="file_write",
    payload={"path": "/app/config.yaml", "summary": "Updated DB connection string"}
)
print(f"Receipt #{receipt.seq}: {receipt.receipt_hash[:16]}...")

# Verify a receipt
result = client.verify(receipt.id)
print(f"Valid: {result.valid}, Chain intact: {result.chain_valid}")

# Get the audit trail
chain = client.get_chain(agent_id="my-agent")
for r in chain.receipts:
    print(f"  #{r.seq} {r.action_type} — {r.timestamp}")

Async Client

from sigil.client import AsyncSigilClient

async with AsyncSigilClient(api_key="sg_your_key_here") as client:
    receipt = await client.attest("api_request", {"endpoint": "/users"})

Environment Variables

Variable	Required	Default	Description
SIGIL_API_KEY	Yes	—	API key for authentication
SIGIL_API_URL	No	http://localhost:8100	Notary API base URL
SIGIL_AGENT_ID	No	from key	Agent identity for chain queries

Development

git clone https://github.com/sly-the-fox/sigil.git
cd sigil
pip install -e ".[dev]"

# Run tests
pytest

# Lint
ruff check .

Links

• Documentation: https://sigil-notary.dev/docs
• Hosted Service: https://sigil-notary.dev
• Issues: https://github.com/sly-the-fox/sigil/issues
• Changelog: CHANGELOG.md

License

MIT