Conciseness

The body is efficient: prerequisites, eight concrete instructions, an error table, and brief examples with no tutorials on concepts Claude already knows. Minor trimmable padding remains — the Overview's second sentence re-enumerates every mechanism the Instructions then repeat, and the Resources list of well-known pattern/library names adds little — so it fits anchor 4 rather than anchor 5's every-token-earns-its-place bar.

Actionability

Instructions are directive and parameterized with real specifics: "rejects new requests with 503 Service Unavailable", "5 failures in 10 seconds", `X-Throttle-Limit`/`X-Throttle-Remaining`/`X-Throttle-Reset` headers, and tier limits (100/25/5). It falls short of anchor 5 because no code or commands appear inline (executable code lives only in references/examples.md) and the referenced "full implementation guide" (references/implementation.md) is a generic API-building outline rather than throttling implementation detail, leaving a gap between promise and payload.

Workflow Clarity

The eight steps form a coherent build order — analyze endpoints, add limiter, priority tiers, circuit breaker, adaptive limits, headers, degradation, then "Write load tests that verify throttle engagement... and recovery behavior" as an explicit validation checkpoint. Anchor 5 is not met because there is no feedback loop (no guidance on adjusting thresholds when load tests fail) and validation appears only at the end rather than as checkpoints during construction.

Progressive Disclosure

The body is a genuine overview with three clearly signaled, one-level-deep markdown links ([`references/implementation.md`], [`references/errors.md`], [`references/examples.md`]), all of which exist as real files. Scored against the actual bundle, structure is good but not ideal: implementation.md is a thin, largely off-topic generic API guide rather than the promised throttling guide, and errors.md covers generic API errors (schema validation, auth) rather than the throttle errors in the body's table — anchor 4's "most content appropriately placed; minor organization gaps".

Specificity

"Implement API throttling policies to protect backend services from overload" names the domain and one concrete action with a goal, but does not enumerate the actual capabilities (concurrency limits, priority queues, circuit breakers, adaptive throttling) that the skill body delivers. This matches anchor 3 (domain plus 1-2 concrete actions, not comprehensive) rather than anchor 4, which expects several specific actions.

Completeness

Both parts are present: a clear "what" ("Implement API throttling policies to protect backend services from overload") and an explicit "when" with trigger phrases ("Use when controlling API request rates... 'throttle API', 'control request rate', or 'add throttling'"). The "when" exceeds anchor 4's expectation, but the "what" is a single thin action with no capability detail, falling short of anchor 5's fully concrete what-and-when example.

Trigger Term Quality

Concrete trigger phrases are given: "throttle API", "control request rate", "add throttling", plus "Use when controlling API request rates". Coverage is good but misses the most common synonym users would say, "rate limiting"/"rate limit", so it does not reach anchor 5's comprehensive synonym coverage; it is clearly above anchor 3's partial coverage.

Distinctiveness Conflict Risk

The API-throttling niche is named, but every trigger term is a throttling variant while the closely adjacent "rate limiting" skill territory is unaddressed — a user asking to "add rate limiting" or "return 429s" would not be clearly routed here versus a generic rate-limit skill. This is anchor 3 (somewhat specific but could still overlap with similar skills) rather than anchor 4's minor-overlap profile.