The router is intentionally short and lean — it points to fragments rather than re-explaining concepts, assumes Claude's competence ("Do not try to apply the citation logic from memory or from this router"), and keeps each section tight. The brief "Why this split" rationale is the only meta-commentary and stays minimal, so every token earns its place.

It gives concrete file paths, a specific script ("Prefer scripts/nature_citation.py"), and concrete runtime parameters (--scope, language, the ~10-segment batch threshold), but no inline executable code or commands — all runnable detail is delegated to bundle files. This matches 'some concrete guidance but incomplete; missing key details' rather than copy-paste-ready instructions.

A clearly numbered 4-step routing protocol ("Follow these four steps every time") with explicit verification guardrails — "never cite a metadata-only candidate without checking the abstract or publisher page" and "Do not invent missing bibliographic fields" — provides a clear sequence with explicit checkpoints. It is not level 2 because validation is stated explicitly, not merely implied.

The references/ layer is well-signaled and one level deep (an on-demand table maps each need to journal-scope.md, ris-endnote.md, script-usage.md, search-strategy.md, all present), but the router's mandatory first instruction — "Read manifest.yaml. Then read every file listed under always_load: static/core/principles.md, chinese-mode.md, workflow.md" — points to files that do not exist in the bundle, breaking the primary navigation path. This prevents the 'easy navigation' of level 3; it is not level 1 because the references/ half is genuinely well organized rather than monolithic.

Lists multiple concrete actions — "splitting long passages into citable segments", "searching only accepted flagship and subjournal titles", "filtering by publication time range", and "exporting one reference-manager-ready output" — matching the anchor for several specific concrete actions.

Explicitly answers both what (segment, search, filter, export) and when, with an explicit "Use this skill whenever..." clause plus a second "Also trigger on..." clause, satisfying the anchor for clear what AND when with explicit triggers.

Covers natural English phrasings ("add citations to a paragraph/manuscript", "export EndNote/RIS/ENW/Zotero RDF") and abundant natural Chinese terms users would say ("补引用", "找引用", "写论文加引用", "加参考文献", "配文献"), giving broad coverage of real user wording.

The Nature/CNS niche is distinctive, but the clause "trigger on general academic-writing citation needs even without the word 'Nature', such as adding references while writing a paper... building a reference list, citation/referencing for academic writing" deliberately broadens it to generic referencing, creating real overlap with a general citation skill. It is not level 3 because the broadened triggers invite conflicts, and not level 1 because the Nature/CNS framing is still a clear niche.