Conciseness

The body is dense and almost entirely domain-specific (capability tables, file locations, scoped API rules Claude cannot know elsewhere), with no padding explaining general concepts. Minor trimming is possible: 'Do not create project mods' appears verbatim at both the location section and the Rules section, and the multi-capability guard sentence is stated in full twice (body text and checklist). That puts it at anchor 4 ('efficient; minor instances that could be trimmed') rather than 5.

Actionability

Concrete, executable guidance dominates: a full `activate(letta)` skeleton with disposer pattern, the capabilities list, exact paths (`~/.letta/mods/foo.ts`), the diagnostics call with severity semantics, and recovery commands (`letta --no-mods`, `LETTA_DISABLE_MODS=1 letta`, `letta mods package ...`). It stops short of anchor 5 because the core code example uses `/* ... */` placeholders in the register calls and detailed recipes are delegated to references, so it is 'mostly executable with minor gaps' rather than copy-paste ready.

Workflow Clarity

The 9-step Workflow has a clear sequence, an explicit validation step ('Do a basic review: valid names, descriptions present, schemas are object schemas, optional capabilities guarded, scoped APIs used, cleanup returned'), a full pre-flight checklist for complex mods, and an error-recovery path ('If a mod breaks startup or command handling, recover with `letta --no-mods`'). Validation plus feedback loop plus checklist matches the top anchor exactly.

Progressive Disclosure

The body is a genuine overview and every capability's detail lives one level deep in real, verified files (references/tools.md, commands.md, providers.md, events.md, permissions.md, ui.md, plan-mode.md, analysis-mode.md, architecture.md — all present in the bundle). Each is loaded conditionally via a 'Load when' decision rule stated twice (workflow step 4 and the References table), making navigation easy. Only a mild nit — the load-when mapping is duplicated — keeps this from being anything less than the top anchor.

Specificity

The description enumerates the full capability surface concretely — "tools, slash commands, local-only model providers, lifecycle/turn events, scoped conversation helpers, panels, and capability-gated behavior" — which is comprehensive coverage of multiple specific actions, matching the top anchor. It exceeds anchor 4 ('lists several specific actions; minor gaps') because no capability listed in the body's decision table is missing from the description.

Completeness

It explicitly answers both questions: what ("Creates and edits trusted local Letta Code mods, including...") and when ("Use when asked to make a mod, add an agent-callable tool...") with concrete trigger phrases. This matches the anchor-5 example structure exactly; anchor 4 ('when' could be more explicit) does not apply since the when-clause lists seven distinct explicit triggers.

Trigger Term Quality

The 'Use when' clause gives natural paraphrased triggers users would actually say: "make a mod", "add an agent-callable tool", "add a slash command", "add a local provider/model adapter", "transform turns", "react to app events", "add lightweight mod UI". Coverage is comprehensive with synonyms (e.g. 'provider/model adapter'); it falls at anchor 5 rather than 4 because no common natural phrasing for this domain is missing.

Distinctiveness Conflict Risk

It carves a clear niche ("trusted local Letta Code mods") and even disambiguates from the nearest neighboring skill — "outside the dedicated /statusline flow" — which the body confirms is a separate skill. Conflict risk is minimal; it is far more distinct than the anchor-4 example ('mostly distinct; minor overlap risk').