Conciseness

Mostly lean: it assumes MPS competence (no basics explained) and uses dense, high-value tables and lists ("Aspect IDs are case-sensitive and create models named `<langModule>.<aspectId>` with no `@` suffix"). Not 5 because the "Loading companion skills" paragraph spends many tokens on conditional loader protocol detail (MCP server vs filesystem catalog branches), and the one framing sentence "An MPS language is a collection of aspects, each a separate model inside the language module" slightly re-explains what the table already shows.

Actionability

Concrete and executable in the main: specific tool names with operation modes ("`mps_mcp_alter_structure` (CREATE_CONCEPTS, CREATE_ENUM, UPDATE_CONCEPT_*)", "`MAKE`, `rebuild:true`", "`runtimeReady:true`") and a specific 9-step authoring order. Not 5 because no example invocation with arguments is shown anywhere — the reader must load a companion skill even to run the first validation call — leaving minor gaps in copy-paste readiness.

Workflow Clarity

Clear sequences with explicit validation checkpoints: the numbered "Validation Flow" assigns each step the error class it catches ("catches concept-level problems", "catches compile errors in generated descriptors"), the "Dependencies and Rebuilds" section mandates re-validation per change type ("all callers ... must be re-validated"), and the closing directive gives an error-recovery loop ("re-check the root cause on the language side ... before patching generated Java"). Authoring order plus validation flow form a complete feedback-looped process.

Progressive Disclosure

Section structure and companion-skill routing are good — a dedicated table column ("Detailed skill") signals one-level-deep siblings, and the skill is appropriately an overview. But scored against the actual bundle: no references/, scripts/, or assets/ exist, so the prominent link "[aspect-model-stereotypes.md](references/aspect-model-stereotypes.md)" ("Authoritative table with usage notes and pitfalls") is a dead end, undermining navigation. Anchor 4 requires references to be mostly clear and functional; a dangling link to the skill's own advertised authoritative reference is a real organization gap, placing this between 3 and 4, at 3 because the missing file makes the stated routing unreliable.

Specificity

Lists multiple concrete capabilities — "index of all aspects (structure, editor, constraints, behavior, typesystem, intentions, actions, generator, textgen, accessories, generation plans)", plus "the recommended authoring order, cross-aspect call patterns, dependency/rebuild rules, and validation flow" — giving comprehensive, not just partial, coverage. Anchor 4 would require minor coverage gaps, but every major capability area of language authoring is explicitly enumerated.

Completeness

Explicitly answers both: what — "Entry point for authoring or modifying an MPS language — index of all aspects ... dependency/rebuild rules, and validation flow"; and when — "Start here when defining a new language or when you do not know which aspect-specific skill applies." Both are concrete with explicit trigger phrases, matching the anchor-5 example structure.

Trigger Term Quality

Good natural keyword coverage: "authoring or modifying an MPS language" plus all the aspect names ("structure, editor, constraints, behavior, typesystem", "generator, textgen") that MPS users would naturally say. Not 5 because common synonyms like "concept", "DSL", or file extensions (.mps, .mpl) are absent; not 3 because the aspect-name coverage is broad and natural rather than partial.

Distinctiveness Conflict Risk

"MPS language" is a clear niche with distinct triggers, and the routing clause "when you do not know which aspect-specific skill applies" explicitly positions it as the router among sibling aspect skills, minimizing wrong-skill triggering. No overlap risk with generic skills since MPS authoring is unambiguous.