Agent Skill Attestation Format (ASAF)

Version: 1.0-draft Status: Draft License: Apache 2.0

This repository contains the specification for the Agent Skill Attestation Format (ASAF), a framework-agnostic format for cryptographically signing, verifying, and revoking AI agent skills and MCP servers.

📖 Read the specification

What This Solves

No major agent registry implements cryptographic signing at the skill package level. ASAF provides:

• Tamper-evident integrity via SHA-256 allowlists
• Publisher authentication via Ed25519 signatures (DSSE v1.0.0)
• Signed revocation with fail-closed install and fail-open runtime modes
• Sigstore compatibility for keyless signing and transparency logs

Reference Implementation

• haldir — TypeScript reference implementation
• sign-action — GitHub Action for CI signing (coming soon)

JSON Schemas

Machine-readable JSON Schemas (JSON Schema Draft 2020-12) are provided in the schemas/ directory. These schemas are automatically generated from the Zod schemas in the Haldir reference implementation.

To validate a .vault/ envelope against the schemas:

npm install -g ajv-cli
ajv validate -s schemas/signature.schema.json -d path/to/.vault/signature.json

Schema updates are synchronized with Haldir releases. If the schemas in this repo diverge from Haldir, CI will fail.

Status

This spec is in draft status (v1.0-draft). The format is implemented and reviewed, but not yet frozen. Breaking changes are possible before v1.0 stable. Feedback welcome via issues.

See VERSIONING.md for details on the versioning and breaking change process.

Contributing

See CONTRIBUTING.md in the org-level repo.

License

Apache 2.0. See LICENSE.