Conciseness

The body is dense and assumes Claude's competence (no boilerplate explanations of Phoenix, evaluators, or basic concepts), but 'persistence is a separate save' is stated nearly verbatim in both loop step 7 and Things To Avoid, and the avoid-list otherwise restates loop points — minor redundancy that could be trimmed. It is not a 5 because not every token earns its place, and not a 3 because there is no padded or unnecessary explanation.

Actionability

Guidance is concrete for an instruction-only skill: it names the exact run fields to inspect ('a chat-style messages array, assistant content parts, tool_calls, or a function_call'), specific deterministic primitives ('exact-match, contains, regex-match, json-distance...'), and a concrete binary label design. It falls short of 5 because there is no worked example — no sample code-evaluator signature, input declaration, or judge-prompt rubric — leaving minor gaps for the most common authoring cases.

Workflow Clarity

The 7-step Authoring Loop has an explicit validation checkpoint ('Calibrate against several representative cases covering the named failure modes'), a feedback loop for error recovery ('When a case mislabels, change one thing — rubric, logic, labels, or case'), and a clear exit condition ('Iterate until the representative cases label correctly'), matching the top anchor. This is a design workflow, not a destructive or batch operation, so no cap applies.

Progressive Disclosure

Sections are well-organized and content is appropriately placed inline for a process skill with no bundle files, but at ~85 lines it exceeds the simple-skill threshold and makes no use of one-level-deep reference files for detail that could be split out (e.g., the judgment-structure ladder or field-topology specifics). Good structure with minor organization gaps rather than the clear reference-split of the top anchor.

Specificity

The description lists multiple concrete actions — 'Author or refine', 'improve an existing one's logic or rubric', 'choose labels', 'decide what to measure on a dataset or experiment' — with comprehensive coverage of the skill's scope and no noticeable gaps, matching the comprehensive-coverage anchor.

Completeness

It explicitly answers both 'what' ('Author or refine a Phoenix evaluator — code or LLM-as-a-judge — that scores a run's output') and 'when' ('Trigger when the user wants to create a new evaluator...') with concrete trigger phrases plus explicit non-triggers, matching the top anchor exactly.

Trigger Term Quality

Natural phrases users would say are well covered ('create a new evaluator', 'improve an existing one's logic or rubric', 'choose labels', 'decide what to measure'), but a few natural variations users might use (e.g., 'judge', 'grading criteria', 'scoring metrics') are missing, placing it just below the comprehensive-with-synonyms anchor.

Distinctiveness Conflict Risk

It carves out a clear niche and explicitly disambiguates against sibling skills ('use playground', 'use experiments', 'use phoenix-error-analysis'), giving minimal conflict risk.