Authoring Cryptographically Signed Skills

Skills extend agent capabilities with tools, prompts, and policy rules packaged in a standard format.

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Skill Layout

A compliant skill repository or folder contains:

my-skill/
├── SKILL.md             # Metadata frontmatter, prompt instructions, and tool declarations
├── skill.yaml           # Cryptographic manifest and Ed25519 signature
├── tools/               # Optional strongly-typed Go tools or MCP definitions
└── rules/               # Embedded CEL policy rules

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Manifest Signing

Sign a skill before publishing to the registry:

# Generate a new Ed25519 author keypair (saved to ~/.ctxsec/identity.key)
ctx keygen

# Sign the skill package
ctx sign ./my-skill --key ~/.ctxsec/identity.key

This calculates SHA256 digests across all files and generates an authoritative Ed25519 signature in skill.yaml.