Conciseness

Nearly every sentence carries iii-specific facts (field tables, limits like "depth 8, 64 nodes, 256 $in items", state transitions, error codes) with no padding of concepts Claude already knows, and version-sensitive material is properly quarantined in the deprecated "Migrating from triggers" section. The main trimmable cost is repetition: the same observe and owner-delivery examples are reproduced in four to five languages inline, so not every token earns its place — matching anchor 4 rather than 5.

Actionability

Fully executable, copy-paste-ready code in TypeScript, Python, Rust, and Go for the core flows ("Register the target first, then observe", complete registerFunction/observe/ready()/dispose() examples), plus concrete filter JSON, a 0.24→0.25 migration table, and error-code tables. The common cases are covered end-to-end; the only gaps are explicitly marked placeholders like "// your validator", which anchor 5 tolerates.

Workflow Clarity

The main flow has a clear sequence ("Register the target first, then observe") with an explicit validation checkpoint — "await failures.ready() // rejects with ObserveRejection (error.code)" — plus a documented state machine (pending → active/error, suspended, disposed) and per-failure error-code tables that enable recovery. It falls short of anchor 5 because, as a reference-style document, several tasks (owner delivery, local dispatch, migration) lack explicit step-by-step sequences with feedback loops; it is above anchor 3 since checkpoints are explicit rather than implicit for the primary workflow.

Progressive Disclosure

No bundle files exist; the single-file body is well-sectioned with clear headers, and bulk detail is offloaded via clearly signaled one-level external links ("Full reference: https://iii.dev/docs/reference/filters", "Full guide: https://iii.dev/docs/creating-workers/observable-functions", "Guide: https://iii.dev/docs/upgrading/from-0-24-x"). It does not reach anchor 5 because nothing is split into local reference files — the ~385-line body inlines material (full filter operator/limits spec, error-code tables, five-language code variants) that could live in references/; it stays above anchor 3 because structure and reference signaling are good.

Specificity

The description lists multiple specific concrete actions with named APIs — "observing iii functions with iii.observe, writing filters, reacting to engine events, writing observable functions with owner delivery (onObserverAdded, obs.emit, obs.call), tuning local dispatch, or migrating from the deprecated registerTrigger / registerTriggerType" — comprehensively covering every major section of the skill body. Not 4: there are no coverage gaps; each capability maps to a concrete, named operation.

Completeness

The explicit "Use when…" clause answers 'when' with concrete trigger scenarios (observing, filter writing, engine events, owner delivery, migration), and the gerund action list embeds a clear 'what'. However, there is no standalone 'what' statement preceding the trigger clause (e.g., "Connects iii functions so one runs when another fires"), so it does not clearly and separately answer both like the anchor-5 example; it is well above anchor 3 because 'when' is explicit, not weakly implied.

Trigger Term Quality

Good keyword coverage with the exact terms an iii user would say: "iii.observe", "filters", "engine events", "local dispatch", and the deprecated "registerTrigger / registerTriggerType" names a migrating user would literally mention. A few natural synonyms are missing (e.g., "subscribe"/"listen to" a function, "run X when Y fails"), which keeps it below the comprehensive-synonym anchor 5 but well above anchor 3.

Distinctiveness Conflict Risk

A clear niche — the iii SDK's observe/observer API — with unique trigger terms ("iii.observe", "onObserverAdded, obs.emit, obs.call", "registerTriggerType") plus an explicit language list ("TypeScript, browser, Python, Rust, and Go"). No realistic overlap with another skill's triggers, matching the clear-niche anchor 5.