Conciseness

Every rule carries project-specific information Claude cannot infer: the 'NavigableOptionList' import path and j/k behavior, the app.py orchestration boundary, the '&:ansi { text-style: dim; }' pairing, the 'ansi_*' ban with theme-variable alternatives, and the Rust TUI parity requirement. There is no padding and no explanation of concepts Claude already knows — the lean, every-token-earns-its-place anchor.

Actionability

Most rules are directly executable, naming exact files ('vibe/cli/textual_ui/widgets/navigable_option_list.py'), classes, TCSS properties, and theme variables ($primary, $surface, $error) plus a doc link. It falls short of fully copy-paste-ready because the tool-header rule ('progressive wording while a call is running, then a settled verb once any result arrives') gives direction without a worked example of the wording.

Workflow Clarity

This is a rule-based conventions skill with no multi-step process and no destructive or batch operations, so no validation cap applies; each rule is an unambiguous directive and the deprecation/parity requirement is stated with a pointer to AGENTS.md. It sits at 4 rather than 5 because the tool-header rendering states rely on interpretation (no before/after example or check of what a correct header looks like).

Progressive Disclosure

The body is under 50 lines, needs no external reference files (none exist in the bundle, and none are warranted), and is cleanly organized into an intro with the deprecation note plus Widgets and TCSS sections. Per the simple-skill guideline this is the well-organized-sections case that scores 5.

Specificity

The description enumerates several concrete activities ('building or styling Textual widgets, writing TCSS rules, working with selectable lists, tool headers, theme variables'), matching the several-specific-actions-with-minor-gaps anchor. It falls short of 5 because notable scope from the body — e.g. the Rust TUI parity requirement — is not reflected, and the what-clause ('Textual TUI widget and TCSS conventions') is more a domain label than an action list.

Completeness

It explicitly answers both questions: what ('Textual TUI widget and TCSS conventions for Mistral Vibe') and when ('Use when building or styling Textual widgets, writing TCSS rules, working with selectable lists, tool headers, theme variables, or UI component layout') with concrete trigger phrases — the anchor-5 pattern.

Trigger Term Quality

Natural terms a user would say are well covered: 'Textual widgets', 'TCSS rules', 'TUI', 'styling', 'theme variables', 'UI component layout'. A few natural synonyms are missing ('terminal UI', '.tcss' files, 'colors'), which fits the good-coverage-with-a-few-missing anchor rather than comprehensive synonym/extension coverage.

Distinctiveness Conflict Risk

'Textual TUI', 'TCSS', and 'Mistral Vibe' define a clear niche with distinct triggers; no plausible overlap with other skills' trigger terms. This is the clear-niche, minimal-conflict anchor.