plurigrid Skill Specification
Formal specification for evolutionarily robust agent skills.
Why This Matters
Skills that follow the spec work across:
- Claude Code (Anthropic)
- Codex CLI (OpenAI)
- Cursor (Anysphere)
- Amp (Sourcegraph)
- Letta (memGPT)
- Future agents
Non-compliant skills break silently or fail validation.
SKILL.md Schema
---
name: skill-name # REQUIRED: lowercase, hyphens, 1-64 chars
description: What and when # REQUIRED: max 1024 chars, no < or >
license: Apache-2.0 # optional
compatibility: Requires git # optional, max 500 chars
metadata: # optional: custom key-value pairs
trit: 0
author: bmorphism
version: "1.0"
allowed-tools: Bash Read # optional, experimental
---
# Body content (Markdown)
Field Constraints
| Field | Required | Rules |
|---|---|---|
name |
✓ | [a-z0-9-]+, no --, no leading/trailing -, max 64 |
description |
✓ | 1-1024 chars, no < or >, includes WHEN to use |
license |
✗ | Short name or file reference |
compatibility |
✗ | Environment requirements, max 500 |
metadata |
✗ | Arbitrary k:v for custom fields |
allowed-tools |
✗ | Space-delimited tool names |
Evolutionary Robustness Patterns
1. Progressive Disclosure
Level 1: name + description (~100 tokens) - loaded at startup
Level 2: SKILL.md body (<5000 tokens) - loaded on activation
Level 3: scripts/, references/, assets/ - loaded on demand
Keep SKILL.md under 500 lines. Move details to references/.
2. Cross-Platform Compatibility
# BAD - platform-specific
allowed-tools: claude_desktop_mcp
# GOOD - generic capability
compatibility: Requires MCP server access
3. Self-Validation Hook
Include validation in your skill:
# scripts/validate.sh
skills-ref validate "$(dirname "$0")/.."
4. Semantic Versioning in Metadata
metadata:
version: "2.1.0"
breaking-changes: "v2.0 changed API"
5. Triadic Classification (GF(3) Extension)
For plurigrid/asi skills:
metadata:
trit: -1 # MINUS: verification, constraint
trit: 0 # ERGODIC: balance, mediation
trit: +1 # PLUS: generation, exploration
Conservation: Σ trits ≡ 0 (mod 3) across compositions.
Directory Structure
skill-name/
├── SKILL.md # Required
├── scripts/ # Executable code
│ └── main.py
├── references/ # Additional docs
│ └── REFERENCE.md
└── assets/ # Static resources
└── template.json
Validation Commands
# Official validator
skills-ref validate ./my-skill
# Codex-rs validator
python3 codex-rs/core/src/skills/assets/samples/skill-creator/scripts/quick_validate.py ./my-skill
# Batch validate
for d in skills/*/; do skills-ref validate "$d"; done
Common Failures
| Error | Fix |
|---|---|
| No YAML frontmatter | Add --- delimiters |
| Unexpected keys | Move to metadata: |
| Angle brackets in description | Remove < and > |
| Name not hyphen-case | Lowercase, hyphens only |
| Description too long | Max 1024 chars |
| YAML colon in value | Quote the string |
Evolution Strategy
- Start minimal - name + description + one paragraph
- Add scripts/ when automation helps
- Add references/ when body exceeds 300 lines
- Add metadata for custom classification
- Validate on every commit via CI