Conciseness

The body never explains concepts Claude already knows and is densely prescriptive, but the missing-input policy is stated three times — once as its own section ('If no spreadsheet tool is attached...'), again nearly verbatim inside the template ('If no spreadsheet integration is available, stop and say...'), and again in 'Required behavioral rules' ('default only when exactly one relevant sheet/table is available') — which is avoidable repetition. This fits 'mostly efficient but includes some unnecessary explanation or could be tightened' better than level 4 (which would require only minor trimming) or level 2 (no known-concept padding, so not 'noticeably verbose' overall).

Actionability

Fully copy-paste-ready for its purpose: a complete system-prompt template with exact refusal strings ('I need access to your spreadsheet first...'), exact receipt formats ('Updated <N> rows in <Sheet name> > <Tab name>, range <A2:D17>'), a six-step worked example with a sample final reply, and a full second builder example. Every instruction is executable as written; this is an instruction-only skill whose guidance is maximally concrete, per the rubric's code_vs_instruction note.

Workflow Clarity

Sequences are explicit with validation checkpoints and feedback loops: read-before-write, dry-run-and-stop for destructive operations, verification by read-back or returned values, a 4-item completion-criteria checklist, and error recovery ('If a row fails to write, report the row number/id and reason'). Because validation/verification steps are explicitly present, the destructive/batch cap at 3 does not apply, and the content matches the level-5 anchor (sequence + explicit validation + feedback loops + checklist).

Progressive Disclosure

No bundle files exist (references/, scripts/, assets/ are absent), and the body references none, so all navigation is internal — that part is clean. However, at ~117 lines with a full inlined system-prompt template plus two worked examples, content that could plausibly live in a separate reference (e.g. the full worked example) is inlined, which is a minor organization gap — the level-4 anchor ('good structure; most content appropriately placed; minor organization gaps') fits better than level 5, and far better than level 3 (sections are well-signaled and nothing is buried).

Specificity

The description lists multiple concrete actions — 'building agents that read or write tabular data', 'updates rows, reads cells, computes totals, generates reports from sheets, syncs data between spreadsheets' — with comprehensive coverage of the authoring-playbook domain across named platforms (Google Sheets, Microsoft Excel, CSV, Airtable, Notion). This matches the anchor 'Lists multiple specific concrete actions; comprehensive coverage'; it is not the level-4 anchor because there are no meaningful coverage gaps.

Completeness

Both parts are explicit: 'what' is 'Authoring playbook for building agents that read or write tabular data' and 'when' is the explicit 'Use this when the user wants an agent that updates rows, reads cells, computes totals...' with concrete trigger phrases. This exactly matches the level-5 anchor example structure.

Trigger Term Quality

Natural terms are comprehensive: product names ('Google Sheets, Microsoft Excel, CSV, Airtable, Notion databases') plus everyday synonyms ('rows, columns, ranges, worksheets', 'spreadsheet') and concrete user goals ('updates rows, reads cells, computes totals, generates reports'). Users would naturally say these when they need this skill; only trivial literal file extensions (e.g. '.xlsx') are absent, which is not enough to drop to level 4.

Distinctiveness Conflict Risk

The niche (authoring spreadsheet-automation agents) is distinct with clear triggers, but phrases like 'reads cells' or 'computes totals' could also fire for a user who merely wants data analyzed in a spreadsheet rather than an agent built, so there is minor overlap risk with a general spreadsheet-processing skill — the level-4 anchor ('mostly distinct; minor overlap risk with closely related skills') is the best fit.