CRAN

AXM reads R extension metadata from a Config/agentExtensions field in the package DESCRIPTION file. This is the two-way linking model applied to the CRAN ecosystem. CRAN reserves Config/ fields for package-specific configuration, so the value travels with your package untouched.

Add a Config/agentExtensions field to DESCRIPTION. Its value is the portable recommendation array encoded as JSON on a single line. Each entry is an extension reference (@owner/<type>/<name>):

Config/agentExtensions: [{"ref":"@examples/packs/r-cran-tinyflags"}]

The DESCRIPTION format is line-oriented, so the JSON must stay on one logical line (continuation lines are indented).

Keep recommendations identity-only — omit versionRange. AXM resolves the reference to the newest matching extension version and pins it in the user's axm.lock. Prefer recommending a single pack so you keep one stable reference while its contents evolve.

Add a semver versionRange only when your package genuinely pairs with a bounded major line of the extension:

Config/agentExtensions: [{"ref":"@examples/packs/r-cran-tinyflags","versionRange":"^1.0.0"}]

On the extension manifest (skill.json, pack.json, subagent.json, …), add a packages array with a CRAN purl. Use the package name from DESCRIPTION as the purl name:

// pack.json
{
  "packages": [{ "purl": "pkg:cran/tinyflags" }],
}

Default to identity-only. Add a VERS versionRange with the cran scheme only when the extension depends on package APIs introduced or removed in a known range:

{
  "packages": [
    {
      "purl": "pkg:cran/tinyflags",
      "versionRange": "vers:cran/>=0.1.0|<1.0.0",
    },
  ],
}

When the CRAN package recommends an extension through the AgentXM Registry and that extension names the package as a companion via its purl, AXM derives official status for the pair — no extra flag. See Official extensions.

The r-cran-lib and r-cran-app directories in polyglot-examples are the working fixtures for everything above. The package publishes a TinyFlags companion pack and recommends it from the Config/agentExtensions field in DESCRIPTION; the pack and each skill declare the package's pkg:cran purl as an identity-only companion package.