Lists multiple specific concrete actions: 'selects frameworks', 'defines data models', 'produces API contracts', and 'creates a dependency-ordered implementation strategy'. These are clear, actionable capabilities.

Clearly answers both what (generate technical design docs with frameworks, data models, API contracts, implementation strategy) AND when (explicit 'Use when...' clause with five specific trigger scenarios).

Includes natural keywords users would say: 'technical design document', 'feature spec', 'planning how to build', 'choosing libraries', 'database schemas', 'Tessl tiles'. Good coverage of both common and domain-specific terms.

Clear niche focused on technical design documents from feature specs. The specific mention of 'Tessl tiles' and the combination of framework selection, API contracts, and implementation strategy creates a distinct profile unlikely to conflict with general coding or documentation skills.

The skill is lean and efficient, assuming Claude's competence throughout. No unnecessary explanations of basic concepts; every section serves a clear purpose with executable commands and specific patterns.

Provides fully executable bash/PowerShell commands, specific jq patterns for JSON manipulation, concrete validation criteria (count FR-XXX patterns, quality score thresholds), and copy-paste ready code blocks throughout.

Clear numbered sequence with explicit validation checkpoints (Spec Quality Gate with score threshold, Constitution Check post-design, Phase Separation Validation). Includes feedback loops (re-run prerequisites after selection, re-validate after auto-fix) and conditional branching for error states.

Well-structured overview with clear one-level-deep references to supporting documents (constitution-loading.md, conversation-guide.md, formatting-guide.md, tessl-tile-discovery.md, phase-separation-rules.md, model-recommendations.md). Content appropriately split between main skill and reference files.