Conciseness

The body is lean and imperative, assumes Claude's competence, and explains only genuinely non-obvious API behavior (e.g., "Treat availability() as a capability check, not a guarantee"). It sits at 4 rather than 5 because the platform-mismatch stop condition is duplicated between Step 2.7 ("must run in a worker, on the server, or against a remote model provider") and the final Error Handling bullet, and Step 1.6's non-web-app stop partially overlaps both.

Actionability

Guidance is fully executable: a copy-paste-ready command ("node scripts/find-writing-assistance-targets.mjs ."), exact API method and option names (availability(), create() with monitor option, AbortController, destroy(), sharedContext vs per-call context), a ready-to-adapt code template in assets/, and named exceptions (NotAllowedError, QuotaExceededError) each paired with a concrete remedy. This matches the 5 anchor rather than 4, which would require gaps in executable detail.

Workflow Clarity

Five clearly sequenced steps culminate in an explicit validation phase (Step 5 re-runs the inventory script, verifies feature detection, tests batch and streaming calls, confirms cancellation and session teardown, and runs build/typecheck/tests). Error handling supplies feedback loops (e.g., QuotaExceededError → shrink sharedContext/context → retry) and the workflow includes stop-and-ask conditions for ambiguity, matching the 5 anchor.

Progressive Disclosure

The body is a concise overview that delegates depth to real, one-level-deep bundle files, each with an explicit read-condition: writing-assistance-reference.md ("before writing code"), examples.md, compatibility.md, and troubleshooting.md ("when ... matters/fail"), plus assets/writing-assistance-session.template.ts and scripts/find-writing-assistance-targets.mjs. All referenced paths exist in the bundle, and navigation is easy, matching the 5 anchor.

Specificity

"Implements and debugs browser Summarizer, Writer, and Rewriter integrations in JavaScript or TypeScript web apps" names multiple concrete actions and the exact APIs, and the trigger clause enumerates specific feature work (availability checks, model download UX, session creation, streaming output, abort handling, permissions-policy constraints). This matches the 5 anchor for comprehensive concrete actions; it is not the 4 anchor because coverage of the domain's tasks is thorough rather than having minor gaps.

Completeness

The 'what' is explicit (implements and debugs browser Summarizer/Writer/Rewriter integrations) and the 'when' is explicit with concrete trigger phrases ("Use when adding availability checks, model download UX, session creation, ..."), plus negative scope ("Don't use for generic prompt engineering, server-side LLM SDKs, or cloud AI services"). This clearly matches the 5 anchor answering both what and when; the 4 anchor would require the 'when' to be less explicit.

Trigger Term Quality

Natural terms users would say include "summarize", "write or rewrite flows", "streaming output", "abort handling", and "model download", giving good keyword coverage. It falls short of the 5 anchor because common synonyms like "built-in AI", "Gemini Nano", "Chrome built-in AI", or file/API extensions users might mention are absent.

Distinctiveness Conflict Risk

It carves a clear niche (browser built-in writing assistance APIs) and explicitly excludes the nearest overlapping domains (generic prompt engineering, server-side LLM SDKs, cloud AI services). Conflict risk with similar skills is minimal, matching the 5 anchor rather than the 4 anchor's 'minor overlap risk'.