CEL Skills

Collection of skills and associated MCP server for working with CEL (Common Expression Language).

1. Install and Configure Skills

To make these skills automatically discoverable and triggerable in Jetski/Gemini Coder across any workspace, inherit the team-level configuration.

Add the following block to your personal configuration file at ~/.gemini/skills.json (create it if it doesn't exist), replacing <path-to-cel-skills> with the path to your cloned repository:

{
  "entries": [
    {
      "path": "<path-to-cel-skills>/skills/cel-authoring"
    },
    {
      "path": "<path-to-cel-skills>/skills/cel-debugging"
    }
  ]
}

2. Testing the Skill Once configured, you can invoke the skills by their name. For example, to test the authoring skill, you can ask your agent:

"Use the cel-authoring skill to create a policy that checks if a user's age is over 18."

The agent will then follow the updated workflow in your SKILL.md, calling cel_create_environment, cel_generate_prompt, and cel_compile as needed.

Releases & Verification

Release binaries for cel-expr-mcp are built automatically on releases with SLSA Level 3 provenance and signed using Sigstore (Cosign) keyless signatures.

Verifying Signatures with Cosign

Using the Sigstore bundle:

cosign verify-blob \
  --bundle checksums.txt.bundle \
  --certificate-identity-regexp 'https://github.com/cel-expr/skills/.github/workflows/release.yml@refs/.*' \
  --certificate-oidc-issuer 'https://token.actions.githubusercontent.com' \
  checksums.txt

Or using the certificate and signature:

cosign verify-blob \
  --certificate checksums.txt.pem \
  --signature checksums.txt.sig \
  --certificate-identity-regexp 'https://github.com/cel-expr/skills/.github/workflows/release.yml@refs/.*' \
  --certificate-oidc-issuer 'https://token.actions.githubusercontent.com' \
  checksums.txt

Verify artifact hashes:

sha256sum --ignore-missing -c checksums.txt

Verifying SLSA Level 3 Provenance

To verify the build provenance using slsa-verifier:

slsa-verifier verify-artifact <cel-expr-mcp-archive> \
  --provenance-path multiple.intoto.jsonl \
  --source-uri github.com/cel-expr/skills \
  --source-tag <tag>