Bilingual Skill Creator

Key references (as of March 2026):

• MMLU-ProX (EMNLP 2025) — cross-lingual performance degrades even between high-resource languages
• Cross-Lingual Prompt Steerability (Zhang et al., Dec 2025) — monolingual prompts reduce language-switching noise, +5-10% robustness
• WMT 2025 — LLM-based systems dominate document-level coherence
• Lokalise 2025 blind study — Claude excels at tone-sensitive translation

If the research landscape has shifted, adapt the methodology accordingly.

Phase 1: Write the source version

Write the complete skill in whichever language is most natural for the content and the author. Stabilize all design decisions, structure, and boundaries before touching the second language.

Run skill-creator's full process on this version: → Load /skill-creator SKILL.md → draft → test → iterate → package

Phase 2: Native rewrite of the target version

The second version is a complete rewrite, not a translation:

• Same design decisions, same section structure
• Phrasing must read naturally — a native speaker should not be able to tell it was derived from another language
• Triggers use the natural domain vocabulary in each language
• Examples are adapted to cultural context if needed

Run skill-creator's process on this version too: → Load /skill-creator SKILL.md → draft → test → iterate → package

Phase 3: Structural alignment check

Verify section-by-section correspondence:

• Every section in the source exists in the target (and vice versa)
• Reference files (templates, examples) are fully in the skill's language
• DESIGN.md is shared between both versions (written in English)

Phase 4: YAML description validation

The description is the trigger mechanism — most critical component:

• Must read naturally in the skill's language
• Must contain keywords the user would spontaneously use
• Zero tokens from the other language (cross-lingual contamination degrades triggering — measured by MMLU-ProX)
• Mental test: "if I type [typical phrase], does this description fire?"

Naming Convention

Two cases:

With suffix (e.g. brief-fr / brief-en): when the trigger keyword is the same word in both languages. The suffix disambiguates.

Without suffix (e.g. passation / handoff): when the trigger keywords are naturally different. The name itself carries the language.

Shared Files

• DESIGN.md — shared between both versions, written in English (architecture document, not user-facing)
• references/* — fully in the skill's own language, never shared

What This Skill Does Not Cover

• Monolingual skills (use skill-creator directly)
• More than 2 languages (would need a selection/routing mechanism)
• Translation of user content (out of scope)

Maintenance

DESIGN.md contains the grounding report for this methodology: research sources, quality label, and adaptation rationale. Read it when updating the Phase 0 references or questioning whether the core hypothesis still holds.