JetBrains MPS is a development environment for creating domain-specific languages, which are programming languages designed for a particular field or task. It provides editors with features such as completion, semantic checks, and type checking, and can generate code in languages including Java and XML.
Borrowing it
Nothing to install: this file belongs to JetBrains/MPS. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/JetBrains/MPS/master/.agents/skills/mps-language-inheritance/SKILL.mdgit clone --depth 1 https://github.com/JetBrains/MPSWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jetbrains/mps/mps-language-inheritance)<a href="https://agentmods.dev/skills/jetbrains/mps/mps-language-inheritance"><img src="https://agentmods.dev/badge/skills/jetbrains/mps/mps-language-inheritance.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00056 | $0.00814 |
| Opus 5 | $0.00028 | $0.00407 |
| Sonnet 5 | $0.00011 | $0.00163 |
| Haiku 4.5 | $0.00006 | $0.00081 |
Grade A, and why
mps-language-inheritance scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 56 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MPS Language and Concept Inheritance
Two layers of inheritance matter in MPS: module-level (one language extends another) and concept-level (concepts inherit superconcepts and implement interface concepts).
Critical Directives
- Concept-level inheritance is realized through module-level extension — different
languageReferenceon a concept and itssuperConceptindicates a cross-language specialization, which usually requires the consumer's language to extend the parent. GET_ALL_SUPERCONCEPTSgives the full transitive closure in a single call — prefer it over recursive walking ofsuperConcept/superInterfaces.IS_SUBCONCEPT_OFis the fastest way to verify a single assignability question; do not enumerateGET_SUB_CONCEPTSand search by hand.
Module-Level Inheritance (Language Extension)
One language can inherit the structure and functionality of another via an "extends" relationship.
- Tool:
mps_mcp_get_project_structure(withincludeDependencies: true). - Workflow: check the
extendedLanguagesfield in the response for the target language. This lists direct parent languages. - Hierarchy tracing: recursively call this tool for each parent to build the full inheritance tree.
Concept-Level Inheritance
Upward Hierarchy (Ancestors)
- Direct ancestors: use
mps_mcp_get_concept_details. The response includes:superConcept: immediate parent concept.superInterfaces: immediate implemented interface concepts.superConceptContainingProjectandsuperInterfaceDetails[*].containingProjectwhen an ancestor comes from another open MPS project and is read-only from the selected project.
- Full closure: use
mps_mcp_query_structurewithGET_ALL_SUPERCONCEPTSto get the complete chain of ancestors and interfaces in one call.
Downward Hierarchy (Descendants)
- Specializations: use
mps_mcp_query_structurewithGET_SUB_CONCEPTSto find all concepts (direct and indirect) inheriting from a base. - Implementations: use
GET_ASSIGNABLE_CONCEPTSto retrieve only non-abstract subconcepts that can be instantiated.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 56 lines · 56 tokens per session scan A 9dd00ac6fe5f
mps-language-inheritance is a skill published in the GitHub repository JetBrains/MPS (1,656 stars, last pushed yesterday), licensed Apache-2.0. It adds 56 tokens to every session and 814 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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