Conciseness

The body is dense with sbx-specific facts ("An npm-type package listed in that metadata is rejected, not translated", "Tokens live in the host OS credential store, never in the sandbox") and never explains what MCP, OAuth, or Cedar are — it assumes Claude's competence, so every token earns its place. Time-sensitive material (docs date, 0.38.0) is quarantined in the dedicated "Last verified" section, matching the rubric's exception, so it cannot be a 4 for padding.

Actionability

Guidance is fully executable: copy-paste console commands ("sbx mcp add slack --url https://slack.example.com/mcp --client-id <ID>", "sbx secret set mcp:slack.client_secret", "sbx mcp load <name> --sandbox <name>", "sbx mcp auth rm <server>"), a flag-to-execution table for all three input shapes of `sbx mcp add`, and complete runnable Cedar policy snippets with the @requireApproval annotation. The common cases are covered concretely; a 4 would require missing key details, and none are evident.

Workflow Clarity

The multi-step flow is clearly sequenced (register → choose static/dynamic at creation → authorize OAuth → attach with `sbx mcp load` → manage/policy), and the "Traps" section serves as an error-avoidance checkpoint for each stage. It is a 4 rather than 5 because there are no explicit validation checkpoints (e.g., verify attachment with `sbx mcp ls`/`inspect`, or confirm authorization via `mcp auth status`) before proceeding — verification is described as available but never prescribed as a step; a 3 would require the sequence itself to have gaps, which it does not.

Progressive Disclosure

The single file has no bundle files (no references/, scripts/, or assets/ exist), and its ~215 lines are broken into well-labeled sections (register, modes, OAuth, gateway tools, management, policy, traps) so navigation is easy. It is a 4 rather than 5 because the Cedar policy and traps material — roughly a third of the body and only relevant to governed orgs — would fit naturally in a one-level-deep reference file, keeping the overview leaner; it is not a 3 because what is present is clearly structured and not buried.

Specificity

The description lists multiple concrete actions — "Register Model Context Protocol servers on the host with sbx mcp and expose them to sandboxes through the built-in MCP gateway" plus the enumerated scopes "registration, OAuth, static vs dynamic mode, and Cedar MCP policy" — giving comprehensive, non-generic coverage of the skill's capabilities in third-person voice. It is not below 5 because no capability area is left to inference, and not below 4 because the enumerated scope list closes the 'minor gaps' a 4 allows.

Completeness

Both halves are explicit: the "what" is stated concretely (register on host, expose to sandboxes via the built-in gateway, covering registration/OAuth/modes/Cedar policy) and the "when" is an explicit multi-clause "Use when adding an MCP server to a sandbox, deciding between --static-mcp and dynamic discovery, wiring OAuth credentials..., or writing a governance policy for MCP tool calls". This matches the anchor where both what and when are answered with concrete trigger phrases; a 4 would mean the "when" was less explicit, which it is not.

Trigger Term Quality

Natural user phrasings are comprehensively covered: "adding an MCP server to a sandbox", "wiring OAuth credentials for a remote server", "writing a governance policy for MCP tool calls", plus exact CLI vocabulary like "--static-mcp" and "dynamic discovery", and both "MCP" and "Model Context Protocol" synonyms. It fits the comprehensive-with-synonyms anchor; a 4 would require noticeably missing natural terms, and none are evident for this domain.

Distinctiveness Conflict Risk

The niche is tightly defined (host-side `sbx mcp` registration and the sbx MCP gateway — not per-client MCP config, which the body explicitly distinguishes), with triggers naming sandbox-specific scenarios. Conflict risk with generic MCP or policy skills is minimal because every trigger is anchored to sbx/sandbox concepts.