Stop shipping the same skill four different ways

What it does

MDA defines a strict Markdown superset — .mda — that compiles into the instruction-file formats major agent runtimes already load: SKILL.md, AGENTS.md, MCP-SERVER.md, and CLAUDE.md. The spec adds structured YAML frontmatter, typed footnote relationships, and cryptographic identity to otherwise plain Markdown, then validates everything against JSON Schema. A reference TypeScript CLI handles the compilation and conformance checking.

The interesting bit

The project treats agent instruction files as software artifacts rather than prose documents. You can declare typed dependencies (requires, depends-on), pin versions and content digests, and attach DSSE-enveloped, Sigstore-anchored signatures so the loading agent can verify tamper-evidence at load time — things standard Markdown frontmatter has no room for.

Key highlights

• One .mda source compiles to drop-in artifacts for Claude Code, Codex CLI, OpenCode, Hermes, OpenClaw, and the broader AAIF ecosystem.
• JSON Schema 2020-12 validation for frontmatter, relationships, and each target schema.
• Typed footnote relationships (parent, child, cites, supports, contradicts, extends) mirrored into machine-readable metadata.
• JCS-canonicalized integrity digests and Sigstore-anchored signatures carried in the frontmatter itself.
• Reference CLI (@markdown-ai/cli) is currently at v1.0.0-rc.3; final 1.0.0 ships when it passes 100% of the conformance suite.

Caveats

• The project is explicitly pre-1.0: the reference CLI must pass the full conformance suite before the spec hits 1.0.0.
• Ecosystem tooling — runtime verifier, dependency resolver, registry, graph indexer — is flagged as future work beyond the core compiler and schemas.
• The CLI is positioned as an authoring and CI checking tool, not an application runtime dependency.

Verdict

Worth a look if you maintain agent skills across multiple runtimes and want dependency graphs or publisher verification. If you only target one platform and don’t care about signed artifacts, it’s likely overkill.