MPS: Skill for Claude Code

MPS Structure Aspect — Concepts

Loading companion skills

Companion names in this skill are lazy dependencies: load only those relevant to the current task. If this skill came from an MCP server, use the host's skill loader to resolve the companion's unique discovered entry URI on the same host-assigned originating server. If the host has no server-backed skill loader, stop and report that limitation; do not silently fall back to a filesystem copy. If this skill came from a filesystem catalog, load the named sibling from that same catalog at <skills-root>/<skill-name>/SKILL.md, even if remote skill loaders are also available. Do not invent a tool name or server endpoint.

Concepts (ConceptDeclaration), interface concepts (InterfaceConceptDeclaration), enumerations (EnumerationDeclaration), and constrained data types (ConstrainedDataTypeDeclaration) are root nodes in a language's structure model. They use the language jetbrains.mps.lang.structure.

Critical Directives

• Implement INamedConcept instead of declaring name directly. A name property declared directly on a concept is an antipattern in MPS — implement jetbrains.mps.lang.core.structure.INamedConcept instead.
• Smart reference check (CRITICAL): before setting a conceptAlias, determine whether the concept is an "Implicit Smart Reference". If it has exactly one mandatory reference and no properties or children of its own, do NOT set a conceptAlias — the concept should be transparent in the editor and completion menu so the user types the target's name directly. Examples: variable references, method calls, routine calls.
• Leave alias empty on transparent collections too (e.g. StatementList).
• Set alias on concepts that can be root — that's how the user reaches them through the new-root menu.
• A language is published unless the user or the task says it is local. On a published language, never delete a feature or make one stricter unless the owner explicitly asks (see the reference below for how); on a local language with instances, do it only together with a Console migration of the existing values. Such a change breaks existing models, and the tools still answer ok:true. See references/language-evolution.md in the mps-aspect-migrations skill root after loading that companion skill from the same origin.
• Always rebuild the language with mps_mcp_alter_nodes MAKE and rebuild="true" after structural changes, so the new concepts are discoverable by runtime tools.