Conciseness

The ~334-line body is mostly original doctrine (not concepts Claude already knows), so much of it earns its tokens, but the core rules are restated repeatedly — 'contract first', 'no edit-in-tandem', and 'just add the field' recur across 'The failure mode', the Stage sections, 'Why this is more than ceremony', and 'The short version' — and passages like 'This is the mechanism that keeps the contract unopinionated...' re-explain points already made. This is 'mostly efficient but includes some unnecessary explanation or could be tightened' rather than the padded verbosity of a 2.

Actionability

For an instruction-only skill the guidance is concrete and near copy-paste ready: the five numbered MUST-contents and three MUST-NOTs for the FEEDBACKS.md artifact, the full verbatim subagent brief (accept/counter-propose/refuse with shipping instructions), the three-outcome verdict handling, and the four procedural patterns each with a named anti-pattern. Minor gaps keep it at 4: the FEEDBACKS.md is specified by requirements rather than shown as a filled-in example, and the worked example's contract fragments are illustrative rather than complete.

Workflow Clarity

The multi-step process is clearly sequenced (write FEEDBACKS.md → spawn the profiled subagent → read the verdict and branch on accept/counter/refuse), with an explicit error-recovery path (refusal is absorbed or escalated, never overridden; don't re-spawn to get a different answer), test checkpoints ('Producer tests run; consumer tests run'), a smells checklist as a stop-and-reset signal, and a 'When NOT to use' gate. Not 5 because validation of the FEEDBACKS.md artifact itself before spawning is not checkpointed, and some steps (tool scoping, escalation rewrite) are described rather than sequenced.

Progressive Disclosure

No bundle files exist (no references/, scripts/, or assets/), so structure rests on the body itself: well-ordered sections, a flow diagram, and one clearly signaled one-level cross-skill reference ('Companion to sdk-design'). The 50-line simple-skill exemption doesn't apply, and the ~334-line body inlines content that could arguably be split (the subagent brief template, the worked example), which keeps it at 4 ('most content appropriately placed; references mostly clear; minor organization gaps') rather than 5.

Specificity

The description names the domain ("the seam between two SDKs (or two sides of one contract) that the same hand writes") and 1-2 concrete actions ("Spawn an adversarial subagent profiled as the producer's maintainer; negotiate the change as a feature request"), but much of its budget goes to abstract framing ("Discipline for the seam", "The failure mode", "The exercise") rather than an enumeration of capabilities. It matches the anchor 'names domain and 1-2 concrete actions, but not comprehensive' — not 4, which requires a list of several specific actions with only minor gaps.

Completeness

The 'what' is clear (keep the joint between two same-author SDKs clean; spawn a producer-maintainer subagent and negotiate as a feature request), but the 'when' is only implied via the applicability list ("applies to a TS package + its consumer, a Rust crate + its WASM binding...") rather than an explicit 'Use when...' trigger clause, which caps completeness at 3 per the judging guidelines. It is above score 2 because the 'what' is concrete, and not 4 because the trigger guidance is implicit rather than explicit.

Trigger Term Quality

Relevant keywords exist ("SDK", "FFI", "IPC", "network protocol", "Rust crate + its WASM binding", "two services sharing a wire format") but they lean technical; the natural phrases a user would say ("I control both sides of this API", "API contract", "package boundary", "breaking change") are largely absent. This is 'some relevant keywords but missing common variations or synonyms' — below 4's 'good keyword coverage', above 2's generic-only.

Distinctiveness Conflict Risk

The niche is clear and specific (seam discipline, producer-maintainer subagent, contract-first sequencing) and mostly distinct, with only minor overlap risk against its own companion ('$sdk-design', 'Companion to $sdk-design' — a closely related skill a user could confuse it with). Not 5 because the companion-skill adjacency is a real, if minor, conflict surface.