Directive Density
Instruction files must contain at least one directive atom — a sentence that tells the agent what to do using imperative or absolute modality. Files with only descriptive prose and no actionable directives have no behavioral effect on the agent.
HighcoredirectionDirectory Layout Documented
The main instruction file must include a section documenting the project's directory layout using a heading like "Structure", "Architecture", "Layout", or "Directory" and containing a tree listing or path references. Without a visible directory map, the agent cannot reliably locate or place files.
HighcorecoherenceDomain Terminology Used
Instruction files must include a section with a heading matching "Terminology", "Glossary", "Terms", or "Domain" that defines project-specific vocabulary. Defining terms prevents the agent from misinterpreting domain-specific words that have different common meanings.
HighcorecoherenceNo Ephemeral Content
Instruction files must not contain ephemeral markers like TODO, FIXME, or WIP. These indicate incomplete content that shouldn't be committed.
HighcorecoherenceExact Filename Convention
Instruction filenames must contain only alphanumeric characters, dots, underscores, and dashes — matching the pattern ^[A-Za-z0-9._-]+$. This prevents encoding issues, shell escaping problems, and path resolution failures across platforms.
HighcorestructureExpected Directories Exist
Configuration files referenced by instruction files must exist on disk. The check verifies that at least one config-type file is present, serving as a gate for directory structure validation.
HighcorestructureExplicit Prohibitions
Instruction files must contain at least one constraint atom — a sentence that tells the agent what NOT to do. Without explicit prohibitions, the agent defaults to its training priors, which may include destructive actions like force-pushing, deleting files, or modifying sensitive configurations.
HighcorecoherenceFrontmatter Block Present
Scoped rule files must begin with a --- YAML frontmatter delimiter as the very first line. The frontmatter block provides metadata like globs and description that controls how the agent discovers and loads the rule file.
HighcorestructureHook Command Has Field
Hook configuration must contain at least one "command" key with a non-empty string value. The check scans for "command": "..." anywhere in the config file.
HighcorestructureHook Handler Has Type
Hook configuration must contain at least one "type" key. Without a type field, the agent cannot dispatch handlers. Agent-specific rules supersede with the valid type enum per agent.
HighcorestructureHook Prompt Has Field
Hook configuration must contain at least one "prompt" key with a non-empty string value. The check scans for "prompt": "..." anywhere in the config file.
HighcorestructureHook Valid Event Types
Config files must contain a "hooks" key. This base rule gates hook validation — agent-specific rules (Claude, Codex, Copilot, Cursor, Gemini) supersede with checks for recognized event names per agent.
HighcorestructureIdentity Fields In Frontmatter
Frontmatter must include identity fields (id, name, or slug) to uniquely identify the instruction file. Without an identity field, the file cannot be referenced, overridden, or tracked by other rules.
HighcorestructureNo Inline Style Rules
Instruction files must not use agent-specific rendering directives like inline styles or scripts.
HighcorecoherenceInstruction Elaboration
Instructions with too few tokens are effectively invisible. Instructions padded with generic filler are weaker than shorter, specific ones. The ideal instruction uses multiple DISTINCT relevant terms — each naming a different concrete aspect of the desired behavior.
HighcoreefficiencyInstruction File Size Limit
Individual instruction files must stay within size limits. Oversized files exceed context windows and degrade agent performance. The check enforces a maximum of 300 lines per file.
HighcoreefficiencyInstruction Ordering
Within a topic, the ORDER of instructions matters. Putting the directive first, reasoning between, and the constraint last is significantly more effective than the natural human pattern of leading with prohibitions.
HighcoredirectionModality Weakness
Hedged instructions ("should", "try to", "consider", "prefer") couple significantly weaker than direct instructions ("do not", bare imperatives).
HighcorecoherenceModular File Organization
A project must contain at least 2 instruction files. Splitting instructions across multiple files keeps each file focused and prevents a single monolithic document from growing unwieldy.
HighcorestructureOutput Format Specified
Instruction files must contain a heading referencing Output, Format, or Display. Specifying expected output formats tells the agent what shape its responses should take.
HighcorecoherencePosition Recency
Instructions at the end of a multi-instruction context dominate. Instructions at the beginning are dramatically weak.
HighcorecoherenceProject Description Present
The root instruction file must describe the project — what it does and who it's for. This anchors the agent's understanding of context and purpose.
HighcorecoherenceScope-Instruction Conflict
Conditional scopes must not name domains whose conventions contradict the instruction. A scope that activates domain knowledge conflicting with the directive makes the instruction less effective than having no scope at all.
HighcorecoherenceSecurity Requirements
The instruction file must contain a section with a heading matching security-related terms (Security, Boundaries, Sensitive, or Access). Without documented security requirements, the agent has no guidance on sensitive files, access restrictions, or security patterns.
HighcorecoherenceShallow Heading Hierarchy
Heading hierarchy must stay at 4 levels or fewer -- no ##### (h5) or deeper headings. Deep nesting makes content harder to scan and signals that the file should be split into smaller files.
HighcorestructureSkill Description Length
The description field in SKILL.md YAML frontmatter MUST be present and concise. The Agent Skills open standard at agentskills.io caps the field at 1024 characters, and GitHub Copilot enforces the same 1024-character cap explicitly. Claude Code caps the combined description + when_to_use text at 1,536 characters in the skill listing. Codex bounds the entire skill list (not the individual description) at roughly 2% of the model context window or 8000 characters. Cursor and Gemini do not document a hard cap but follow the open standard. A description that respects 1024 characters is portable across every agent; long descriptions waste context tokens and risk truncation in the agents that enforce the tighter cap. Front-load the key use case.
HighcorestructureSkill No README
Skill directories MUST NOT contain a README.md file. All skill documentation belongs in SKILL.md — agents discover and load SKILL.md as the skill entry point. A separate README.md splits documentation across two files and the extra file is never loaded.
HighcorestructureTech Stack Declared
The root instruction file must contain a heading matching technology terms (Stack, Tech, Language, Runtime, or Framework). Declaring the tech stack prevents the agent from guessing or suggesting incompatible technologies.
HighcorecoherenceTotal Instruction Size Limit
The aggregate size of all instruction files in the project must not exceed 100 KB (102,400 bytes). Exceeding this limit wastes context budget and dilutes the effectiveness of individual instructions.
HighcoreefficiencyVcs Tracked
All instruction files must be tracked in git. Untracked instruction files create divergence between collaborators -- each developer's agent sees different instructions.
Highcoregovernance