Entry point for authoring or modifying an MPS language — index of all aspects (structure, editor, constraints, behavior, typesystem, intentions, actions, generator, textgen, accessories, generation plans), the recommended authoring order, cross-aspect call patterns, dependency/rebuild rules, and validation flow. Start here when defining a new language or when you do not know which aspect-specific skill applies.

Analyze an MPS language by name — discover concepts, properties, references, children, aspects (editor/constraints/behavior), and metadata. Use when investigating an unfamiliar language, exploring concept structure, or finding sample nodes to use as templates for JSON blueprints.

Use when authoring XML documents as MPS root nodes or building XML-generating generator templates with jetbrains.mps.core.xml — covers XmlFile, XmlDocument, prolog (XML declaration, DOCTYPE, processing instructions, comments), elements, attributes, CDATA, entity references, and macro attachment via the smodelAttribute role for templates that emit XML output.

Use when authoring or modifying MPS IDE plugins — code that integrates with the MPS / IntelliJ host IDE shell. Covers ActionDeclaration, ActionGroupDeclaration, ToolDeclaration/TabbedToolDeclaration (dockable tool windows), KeymapChangesDeclaration (shortcuts), PreferencesComponentDeclaration (settings pages), EditorTab+Order (concept editor tabs), InterfaceGroup (bootstrap wrappers around external groups), NonDumbAwareActions, IdeaConfigurationXml, ApplicationPluginDeclaration/ProjectPluginDeclaration/StandalonePluginDescriptor (lifecycle hooks). Uses jetbrains.mps.lang.plugin and jetbrains.mps.lang.plugin.standalone. Trigger terms: action group, tool window, menu item, MainMenu, EditorPopup, NodeActions, ModelActions, ModuleActions, ProjectViewPopupMenu, MPS plugin solution, ActionInstance, ModificationStatement, DataKey, MPSCommonDataKeys, MPSDataKeys, dumb-aware, project.tool<...>, project.preferenceComponent<...>, application plugin<...>, project plugin<...>.

Create or refresh project-local DSL skills under `.agents/skills/<dsl-name>-dsl/` for one or more MPS languages after discovering concepts, sandbox examples, JSON blueprints, references, or gotchas.

Use when bundling a new plain Java/Kotlin plugin into MPS distribution archives, debugging packaging/layout issues in `build/mps*.xml`, tracing where per-plugin artefacts end up, or editing `plugins/mps-build/solutions/mpsBuild/models/build.mps` (the source of truth that generates every `build/mps*.xml`). The skill covers the generated Ant pipeline, plugin-to-distribution wiring, and the per-plugin / aggregator / distribution layers.

Use when running or generating MPS Console code, or when writing `jetbrains.mps.lang.smodel.query` queries anywhere in MPS (intentions, behavior, actions, generator queries, plain BaseLanguage). Covers the console command languages (`jetbrains.mps.console.base` / `ideCommands` / `internalCommands` / `scripts`): `BLCommand` / `BLExpression`, the `#print*` / `#show` result printers, IDE commands (`#make` / `#clean` / `#removeGenSources` / `#reloadClasses` / `#stat` / `#showGenPlan` / `#showBrokenRefs`), `#exec` / `forEach` / `refactor` scripts. Covers the smodel query language: `#nodes` / `#references` / `#models` / `#modules` / `#instances` / `#usages`, the `with`-statement scope wrapper, scopes (`project` / `editable` / `global` / `visible` / `modules` / `models` / `custom`) and query parameters (`scope` / `exact` / `r/o+`). Also how to insert, read, recall, and run console commands with `mps_mcp_insert_console_command_from_json`, `mps_mcp_get_current_editor_root_node(source="console")`, `mps_mcp_get_console_history`, `mps_mcp_recall_console_command`, and `mps_mcp_run_console_command`.

Use when authoring or modifying MPS Build Language scripts (`BuildProject` roots) — the declarative DSL that generates Ant `build.xml` to package MPS language plugins, IDEA plugins, plain Java modules, standalone IDE/RCP distributions, module tests, or `run code from solution` tasks. Covers build solution setup, macros, project/external/Java dependencies, MPS module declarations (`BuildMps_Language` / `_Solution` / `_Generator`), groups, layouts, IDEA-plugin declarations, MPS settings, and the workflow language. Trigger terms: `BuildProject`, `BuildMps_*`, `BuildLayout_*`, `jetbrains.mps.build`, `build.mps` solution, `internalBaseDirectory`, `compactBuildScriptFileName`, Ant target generation, `mps_home`, `idea_home`.

Structured MPS bugfix workflow driven by a YouTrack issue ID — preflight tool checks, version/branch derivation, parallel-agent problem analysis, solution design, branch creation, implementation, review, and YouTrack updates. Use when the user invokes "/bugfix", asks to "fix a bug", "work on a bug", "investigate an issue", or provides a YouTrack issue ID.

Author and edit MPS `jetbrains.mps.baseLanguage` (Java) nodes — choose between the Java parser and JSON AST blueprints, map Java syntax to baseLanguage concepts/roles, harvest persistent member references, and validate. Use when writing class/method bodies, fields, expressions, statements, or any Java/BaseLanguage code inside MPS models, especially when BaseLanguage extensions (smodel, closures, collections) are involved.

Use when authoring or debugging MPS typesystem — inference rules (`typeof :==: / :<=: / :>=:`), `SubtypingRule`, `ComparisonRule`, `InequationReplacementRule`, `SubstituteTypeRule`, `WhenConcreteStatement` blocks, `NonTypesystemRule` checking rules, `TypesystemQuickFix`, error/warning/info reports with `messageTarget` highlighting and quick-fix wiring (`helginsIntention`), and shared BaseLanguage helpers in the typesystem model. Reach for this skill whenever the task involves editing `<lang>/languageModels/typesystem.mps`.

Use when authoring or debugging MPS TextGen — concept-to-plain-text serialisation for languages whose final output is text (source files, config, scripts, DDL, XML, markdown). Covers `ConceptTextGenDeclaration` roots, `append` / `indent buffer` / `with indent` statements, text layout areas, context objects (e.g. imports sets), attributes, the base text gen component (`LanguageTextGenDeclaration`), binary `write`, `found error`, and the indentation-buffer model. Reach for this skill whenever the task involves editing `<lang>/languageModels/textGen.mps`.

Define concepts, interface concepts, enumerations, and constrained data types in an MPS language's `structure` aspect. Covers smart-reference detection, alias rules, cardinality, INamedConcept usage, bulk creation, and the full `mps_mcp_alter_structure` / `mps_mcp_query_structure` reference. Use when authoring or modifying a language's structure model.

Use when authoring or debugging MPS migration scripts that upgrade user models after a language definition changes — covers jetbrains.mps.lang.migration (MigrationScript class-based, PureMigrationScript declarative, MoveConcept/MoveContainmentLink/MoveReferenceLink/MoveProperty, ordering via OrderDependency, data exchange via putData/getData, RefactoringLog, ConceptMigrationReference) and jetbrains.mps.lang.script Enhancement Scripts (MigrationScript with MigrationScriptPart_Instance, ExtractInterfaceMigration, FactoryMigrationScriptPart, CommentMigrationScriptPart) — when a model needs version-gated upgrade, concept rename or removal, link or property rename, instance-level transformation, or composition of migration steps.

Use when defining or editing MPS intentions (the Alt+Enter context-action aspect) — adding `IntentionDeclaration` roots, parameterized or surround-with variants, description/isApplicable/execute blocks, child-filter functions, factory-initialized AST splicing, or debugging why an intention is not offered. Lives in the language's `intentions` model and uses `jetbrains.mps.lang.intentions`.

Use when defining or modifying MPS generators — author a generator module, add or edit root/reduction/weaving/pattern mapping rules, attach template macros ($COPY_SRC, $LOOP, $IF, $PROPERTY, $REF, $SWITCH, $MAP_SRC, $WEAVE, $INSERT, $LABEL, $TRACE, $VAR), wire mapping labels, build template switches, write pre/post mapping scripts, navigate `genContext`, or debug "rule didn't fire", missing references, empty output, infinite reduction loops, and generated-Java compile failures.

Use when defining or modifying an MPS generation plan — explicit ordering of generators, checkpoints for cross-model reference resolution, forks for parallel branches, IncludePlan composition, conditional PlanContribution activation, ParameterEquals/ConceptListSelector fork selectors, and InitModelAttributes for targetFacet routing. Apply when working with @genplan models, the jetbrains.mps.lang.generator.plan language, attaching plans via DevKits or the Custom generation facet, or debugging cross-model mapping label resolution.

Use when creating or changing MPS editor definitions — the overall workflow from scaffolding a `ConceptEditorDeclaration` through componentizing reusable `EditorComponentDeclaration`s, refining cell models and cell layouts, applying style sheets and indent-layout style items, wiring smart references, leveraging inheritance via super-concepts and interfaces, inspecting (`print_node_json`, `show_node_representation`) and validating (`check_root_node_problems`). Covers `jetbrains.mps.lang.editor` cell models (`CellModel_RefNode`/`CellModel_RefNodeList`/`CellModel_RefCell`/`CellModel_Property`/`CellModel_Constant`), layout choices, and JSON blueprints for common editor shapes. For the non-layout side (action maps, keymaps, transformation/substitute menus) use `mps-aspect-editor-menus-and-keymaps`.

Use when authoring the **non-layout** parts of the MPS editor aspect — what happens when the user types, presses a key, triggers completion, pastes, or invokes a context action. Covers action maps (`CellActionMapDeclaration`), cell keymaps (`CellKeyMapDeclaration`), transformation menus (`TransformationMenu_Default` / `_Named` / `_Contribution`), substitute menus (`SubstituteMenu_Default` / `SubstituteMenu` / contributions), side transforms (LEFT/RIGHT), legacy cell menus, paste wrappers and copy-paste handlers (in the actions language), completion styling, reference presentation, two-step deletion, and the editor selection API. Trigger terms: `actionMap`, `keyMap`, `delete_action_id`, `transformationMenu`, `substituteMenu`, `Ctrl+Space`, `Ctrl+Alt+B`, side transform, paste wrapper, completion styling, `PasteWrappers`, `CopyPasteHandlers`. For the **layout** side (cells, layouts, style sheets) use `mps-aspect-editor` instead.

Use when defining or debugging MPS dataflow builders for a concept — control/data flow declarations that drive reachability analysis and variable-use checking. Covers DataFlowBuilderDeclaration, BuilderBlock, emit instructions (code for, jump, ifjump, label, read, write, ret, mayBeUnreachable), positions (AfterPosition, BeforePosition, LabelPosition), the jetbrains.mps.lang.dataFlow language, the NodeParameter implicit, BL+smodel usage inside builder bodies, and IBuilderMode for advanced analyses such as nullable/non-null tracking.