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.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/jetbrains/mps/mps-lang-core-xmlnpx skills add JetBrains/MPS --skill mps-lang-core-xmlgit 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-lang-core-xml)<a href="https://agentmods.dev/skills/jetbrains/mps/mps-lang-core-xml"><img src="https://agentmods.dev/badge/skills/jetbrains/mps/mps-lang-core-xml.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 | $0.00080 | $0.00966 |
| Opus 5 | $0.00040 | $0.00483 |
| Sonnet 5 | $0.00016 | $0.00193 |
| Haiku 4.5 | $0.00008 | $0.00097 |
Grade A, and why
mps-lang-core-xml 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 6d 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 — 44 lines — stays where its author put it; the contents beside it link to each section on GitHub.
jetbrains.mps.core.xml Language
jetbrains.mps.core.xml is an MPS language for authoring and generating XML documents inside MPS models. It is used either for direct XML authoring (an XmlFile root holds a complete document) or for generator templates (an XmlFile carries RootTemplateAnnotation and macros via smodelAttribute child roles).
Language reference: l:479c7a8c-02f9-43b5-9139-d910cb22f298:jetbrains.mps.core.xml
Critical Directives
- Wrap everything in
XmlFile → XmlDocument.XmlFileis the only rootable concept.XmlDocument.rootElementhas cardinality 1 — put the root there, not incontent. XmlPrologis optional (0..1). Omit it entirely when no prolog is needed.- Attribute values are lists of
XmlValuePart. A plain string is a singleXmlTextValue. An attribute with novaluechildren renders as a valueless (boolean) attribute. - Property name asymmetry:
XmlText/XmlSingleLineTextuse the propertyvalue.XmlTextValue(attribute value part) uses the propertytext. Do not swap them. - In generators, macros go in the
smodelAttributechild role of the node they annotate — not as siblings incontentorattributes. - Subclass the base types. Extend
XmlBaseAttribute(notXmlAttribute) andXmlBaseElement(notXmlElement) when defining custom concepts for derived languages. - Do not hand-edit serialized
.mpsfiles. Use MPS MCP node tools for all changes.
Common-Path Workflow
- Add
jetbrains.mps.core.xmlas a used language on the target model. For generator templates, also addjetbrains.mps.lang.generator. - Create an
XmlFileroot node with aname. Thenameis the template/document identifier, not the output filename. - Add an
XmlDocumentchild in roledocument. Optionally add anXmlPrologfor declarations/comments/PIs. - Build the document tree under
XmlDocument.rootElementand the innercontentlists. - For generator templates, attach
RootTemplateAnnotationto theXmlFileviasmodelAttribute, and attach macros (PropertyMacro,LoopMacro,CopySrcNodeMacro, …) to inner nodes via theirsmodelAttributerole. - Validate with
mps_mcp_check_root_node_problems.
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 6d ago First seen · 44 lines · 80 tokens per session scan A b76d4c2ace3b
mps-lang-core-xml is a skill published in the GitHub repository JetBrains/MPS (1,656 stars, last pushed today), licensed Apache-2.0. It adds 80 tokens to every session and 966 once invoked, about $0.0004 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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