Conciseness

The body is dense with sbx-specific, non-inferable facts (deny-by-default egress, the `--` argument merge rule, create-time-only flags) and never explains concepts Claude already knows, so it is well above the 'mostly efficient' anchor. It falls short of 5 only because a few passages over-explain reasoning that could be trimmed — e.g. the rationale for pre-loosened agents ('The reasoning is that the microVM *is* the boundary, so the prompts guard nothing…') and the multi-sentence trust-boundary discussion of the shared skills store.

Actionability

Nearly every section is copy-paste-ready shell commands with inline comments, covering the common cases concretely: lifecycle (`sbx run claude --name my-sandbox ~/my-project`), CI login (`echo "$DOCKER_PAT" | sbx login --username <docker-id> --password-stdin`), SSH commit signing, policy, ports, and the YAML kit fork example. This matches 'Fully executable; copy-paste ready code or commands; specific examples cover the common cases'.

Workflow Clarity

Multi-step processes are clearly sequenced with explicit validation checkpoints and feedback loops: SSH signing is split into 'Load the key on the **host**, then configure Git **inside**'; 'The loop' section is literally a validate-fix-retry cycle (`sbx policy log` → `sbx policy allow network <host>` → retry); and `sbx kit validate`, `sbx policy check`, `sbx skills import --dry-run`, and reading back OS-assigned ports from `sbx ports` serve as pre-flight checks. Diagnose commands are ordered ('Try them in that order').

Progressive Disclosure

The body is a clear 80%-case overview with well-signaled, one-level-deep references that exist on disk ([references/credentials.md](references/credentials.md), [references/discrepancies.md](references/discrepancies.md)), a 'Where the detail lives' routing table delegating deeper topics to named sibling skills, and no nested-reference chains. This matches 'Clear overview with well-signaled one-level-deep references; content appropriately split; easy navigation'.

Specificity

The description enumerates multiple concrete capabilities — 'choosing an agent, passing it flags, git workspace modes, ports, secrets, network policy, and sharing host skills into a sandbox' — which comprehensively covers the skill's operating surface, matching the top anchor ('Lists multiple specific concrete actions; comprehensive coverage'). It is not a 4 because there are no noticeable coverage gaps in the action list.

Completeness

It explicitly answers both questions: the 'what' is 'Run and operate Docker Sandboxes' with a concrete capability list, and the 'when' is an explicit 'Use when starting or re-attaching to a sandbox, picking between the built-in agents, signing in from CI, copying files in or out, or reaching for the right sbx command' with concrete trigger phrases. This is the anchor-5 example pattern verbatim in structure.

Trigger Term Quality

Natural trigger phrases users would actually say are comprehensively covered: 'starting or re-attaching to a sandbox', 'picking between the built-in agents', 'signing in from CI', 'copying files in or out', plus product synonyms ('Docker Sandboxes', 'sandbox', 'sbx'). This matches the top anchor's comprehensive synonym coverage; nothing common is missing.

Distinctiveness Conflict Risk

'Run and operate Docker Sandboxes' carves a clear niche (operating sandboxes) distinct from the sibling skills it implies (building templates/kits, diagnosing, governing), and the 'sbx' product terms are unambiguous, so minimal conflict risk. Not a 4: no meaningful overlap with closely related skills is introduced by the wording.