Cryptographic tool schema verification for AI agents and MCP servers. Prevent "MCP Rug Pull" attacks with ECDSA signatures, DNS-anchored trust, and TOFU key pinning.

Read the Documentation →

SchemaPin lets tool developers sign their schemas and skill folders with ECDSA P-256 keys, and lets AI agents verify that schemas haven't been tampered with. Public keys are discoverable via .well-known/schemapin.json (RFC 8615), and Trust-On-First-Use pinning protects against future key substitution.

• ECDSA P-256 + SHA-256 cryptographic signatures
• .well-known discovery for public keys (RFC 8615)
• TOFU key pinning to prevent key substitution attacks
• Key revocation with standalone signed revocation documents and structured reasons
• Trust bundles for offline and air-gapped verification
• Pluggable resolvers — .well-known, local file, trust bundle, or chain
• Skill folder signing for AgentSkills (SKILL.md + file manifests)
• Cross-language — Python, JavaScript, Go, and Rust implementations

v1.4.0-alpha.2 (all four languages): three additive optional features — signature expiration (expires_at) with degraded-not-failed verification, DNS TXT cross-verification at _schemapin.{domain} for second-channel trust, and schema version binding (schema_version + previous_hash) for opt-in lineage chain enforcement that defends against rug-pull substitutions. v1.3 verifiers ignore the new fields; v1.4 verifiers handle both. The remaining v1.4 items (canonicalization id, A2A context, A2A trust bundles, scan-aware sigs, cross-agent schema cache) ship in subsequent alphas before stable v1.4.0.

from schemapin.crypto import KeyManager
from schemapin.utils import SchemaSigningWorkflow, SchemaVerificationWorkflow
# Sign a schema
private_key, public_key = KeyManager.generate_keypair()
signer = SchemaSigningWorkflow(KeyManager.export_private_key_pem(private_key))
signature = signer.sign_schema({"name": "my_tool", "parameters": {...}})
# Verify a schema
verifier = SchemaVerificationWorkflow()
result = verifier.verify_schema(schema, signature, "example.com/my_tool", "example.com")

Getting Started Guide →

pip install schemapin

npm install schemapin

go install github.com/ThirdKeyAi/schemapin/go/cmd/...@latest

[dependencies]
schemapin = "1.3.0"
# v1.4.0-alpha.2 is also published — opt in for signature expiration,
# DNS TXT cross-verification, and schema version binding:
# schemapin = { version = "1.4.0-alpha.2", features = ["dns"] }

python/ # Python SDK (PyPI: schemapin)
javascript/ # JavaScript SDK (npm: schemapin)
go/ # Go SDK
rust/ # Rust SDK (crates.io: schemapin)
server/ # Production .well-known endpoint server

MIT — Jascha Wanger / ThirdKey.ai