Conciseness

Prose is lean and assumes competence — no padding explaining what code mode or sandboxing is, and driver trade-offs are compressed into a comparison table. The main tightening opportunity is the identical 9-line fetchWeather toolDefinition repeated in four separate examples. Not 5 because that repeated boilerplate is a noticeable token cost; not 3 because outside the repetition there is almost no over-explanation.

Actionability

Every section ships complete, copy-paste-ready TypeScript: full server route handlers for createCodeModeTool, createCodeMode, and codeModeWithSnippets; driver config blocks with defaults annotated inline; a complete React component for client-side event handling; and concrete wrong/right pairs for each common mistake. Covers the common cases comprehensively.

Workflow Clarity

Setup follows a clear sequence (define tool → create code-mode tool → wire into chat), the driver-selection table guides the key decision point, and Common Mistakes supplies validation checkpoints for a genuinely risky operation (probeIsolatedVm before using isolated-vm, explicit finite timeout, keep secrets out of the sandbox). Not 5 because the main setup flow itself has no explicit validate/recover feedback loop — checkpoints live in a separate mistakes section rather than the workflow steps.

Progressive Disclosure

The single SKILL.md is ~580 lines with no bundle files (references/, scripts/, assets/ do not exist), so all content — including the sizable client-integration React component, snippet storage details, and lazy-tools subsection — is inlined in one file. Section headers and numbered patterns give it real structure, which lifts it above 2, but content that clearly belongs in separate reference files (client integration, driver reference) is inline with only one cross-skill pointer. Not 4 because there are no well-signaled one-level-deep references at all.

Specificity

Lists multiple concrete capabilities with named APIs: 'createCodeModeTool() with isolate drivers (createNodeIsolateDriver, createQuickJSIsolateDriver, createQuickJSBunIsolateDriver, createCloudflareIsolateDriver)', 'codeModeWithSnippets() for persistent snippet libraries', 'snippet storage (FileSystem, LocalStorage, InMemory, Mongo)', and 'code_mode:* custom events in useChat' — comprehensive coverage of the skill's surface. Not 4 because coverage spans every major feature area of the skill rather than having minor gaps.

Completeness

The 'what' is clear and detailed (sandboxed execution, drivers, snippets, storage, events), but there is no 'Use when...' clause or equivalent explicit trigger guidance anywhere in the description. Per rubric guideline, a missing 'Use when' clause caps completeness at 3 even with a clear 'what'.

Trigger Term Quality

Relevant domain keywords exist ('LLM-generated TypeScript execution', 'sandboxed environments', 'snippet libraries', 'trust strategies'), but most terms are exact API/function names (e.g. 'createQuickJSBunIsolateDriver') rather than phrases a user would naturally say. Natural variations like 'code mode', 'run LLM code safely', or 'isolates' are missing. Not 4 because the keyword set is skewed toward jargon over natural user language; not 2 because several genuinely relevant domain terms are present.

Distinctiveness Conflict Risk

Naming library-specific APIs (codeModeWithSnippets, code_mode:* events) creates a clear niche that few other skills would match. Not 5 because it overlaps with the closely related tool-calling skill in the same library ('Code Mode is always used on top of a chat experience'), and the description gives no trigger guidance to disambiguate when this skill should fire instead of a sibling.