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RFC-0000: skillc — A Development Kit for Skill Writers

Version: 0.1.0 | Status: normative | Phase: stable

1. Summary

[RFC-0000:C-VISION] Vision (Informative)

skillc is a development kit for Agent Skills — the open format for extending AI agent capabilities with specialized knowledge and workflows.

Agent Skills define what a skill is: a folder with a SKILL.md file containing metadata and instructions. skillc provides the how: tooling to author, validate, optimize, and instrument skills throughout their lifecycle.

Where the Agent Skills specification ends, skillc begins.

Since: v0.1.0

2. Motivation

[RFC-0000:C-PROBLEM] Problem Statement (Informative)

The Agent Skills format solves the consumption problem: a simple, portable way for agents to discover and load specialized knowledge. But skill authoring remains ad-hoc.

Today, skill writers:

  • Write skills blind — No data on which sections agents actually read
  • Guess at structure — No tooling to validate or optimize content organization
  • Can’t iterate effectively — No feedback loop between publishing and agent usage
  • Manage skills manually — No registry, no build pipeline, no version tracking

The Agent Skills spec recommends keeping SKILL.md under 500 lines and using progressive disclosure, but provides no tooling to enforce or automate these practices.

Skill writers need a development kit.

Since: v0.1.0

3. Scope

[RFC-0000:C-SCOPE] Scope (Informative)

skillc complements the Agent Skills ecosystem by providing:

  • Scaffolding — Initialize properly-structured skill directories
  • Validation — Check skills conform to the spec (extends skills-ref validate)
  • Compilation — Generate optimized stubs that enforce size limits and progressive disclosure
  • Instrumentation — Trace agent access to skill content (sections read, files opened)
  • Analytics — Aggregate usage data to identify high-value vs. ignored content
  • Registry — Track skills across source and runtime locations

skillc is a local CLI tool. It works with the existing Agent Skills format — no proprietary extensions, no lock-in.

Since: v0.1.0

[RFC-0000:C-NONGOALS] Non-Goals (Informative)

skillc does not:

  • Define a new skill format — We build on Agent Skills, not compete with it
  • Replace skills-ref — We extend validation, not duplicate it
  • Host or distribute skills — Publishing is out of scope for v0
  • Modify agent behavior — Agents consume skills normally; instrumentation is transparent
  • Require infrastructure — No servers, no cloud, no accounts

Since: v0.1.0

4. Principles

[RFC-0000:C-PRINCIPLES] Design Principles (Informative)

1. Extend, don’t reinvent Agent Skills is an open standard with broad adoption. skillc adds tooling; it doesn’t fork the format.

2. Observability unlocks iteration You can’t improve what you can’t measure. Instrumented access is the foundation for data-driven skill refinement.

3. Progressive disclosure by default The spec recommends it; skillc enforces it. Compiled stubs expose structure without dumping content.

4. Local-first, zero infrastructure skillc runs on your machine. Skills are files. No accounts, no network, no vendor lock-in.

5. Minimal viable tooling Start with the smallest useful toolkit. Add capabilities only when clearly needed.

Since: v0.1.0

5. Compatibility Guarantees

[RFC-0000:C-COMPAT-FORMAT] Format Compatibility (Normative)

skillc MUST accept any directory that conforms to the Agent Skills specification.

skillc MUST NOT require proprietary extensions, additional metadata fields, or non-standard file structures to function.

Since: v0.1.0

[RFC-0000:C-COMPAT-OFFLINE] Offline Operation (Normative)

Core skillc functionality — authoring, validation, compilation, instrumentation, and analytics — MUST operate without network access.

Optional features MAY require network access, but MUST be explicitly opt-in and MUST NOT be required for basic skill development workflows.

skillc MUST NOT require accounts or authentication for core functionality.

Since: v0.1.0

[RFC-0000:C-COMPAT-PORTABLE] Portability (Normative)

Skill source directories managed by skillc MUST remain valid Agent Skills per the specification.

Compiled stubs MAY instruct agents to use skillc gateway commands for content access. Instrumented tracing is only available when agents access content through skillc.

skillc MAY provide options to include source references or mappings in compiled output, enabling fallback access when skillc is unavailable. The mechanism for source mapping is implementation-defined.

Since: v0.1.0

Changelog

v0.1.0 (2026-01-30)

Initial release