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-bugfixnpx skills add JetBrains/MPS --skill mps-bugfixgit clone --depth 1 https://github.com/JetBrains/MPSWhat 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 | $0.00087 | $0.01497 |
| Opus 5 | $0.00044 | $0.00749 |
| Sonnet 5 | $0.00017 | $0.00299 |
| Haiku 4.5 | $0.00009 | $0.00150 |
Grade A, and why
mps-bugfix 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 3d 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 — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MPS Bugfix Workflow
You are guiding a structured bugfix process for the JetBrains MPS project. Follow each phase in order. Never skip phases or start implementation before the user gives an explicit command to do so.
The issue to fix: $ARGUMENTS
Critical Directives
- Never start implementing code before the user gives explicit approval. Wait for "implement", "go ahead", "start coding", "do it", etc.
- Never skip Phase 0 preflight. Missing YouTrack MCP, IDEA MCP, or the platform project changes how you should proceed; surface the gap before touching code.
- Prefer fixing the true source of truth (MPS model/generator) over patching generated code.
- Use IDEA MCP for Java/Kotlin navigation and inspection; use MPS MCP for MPS model edits.
- Validate after each logical change —
mcp_idea_get_file_problemson modified files, build affected module, run smallest relevant test suite.
Phase 0 — Pre-flight Checks
Verify all required tools and inputs before doing any work.
0.1 — Issue ID
If $ARGUMENTS is empty, stop immediately and ask:
Which YouTrack issue should I work on? Please provide the issue ID (e.g.
MPS-12345).
Do not continue until a valid-looking issue ID is supplied.
0.2 — YouTrack MCP
Check that the YouTrack MCP server tools are available in this session (by attempting to call get_issue).
If they are not available:
YouTrack MCP is not connected. Please start the YouTrack MCP server and retry.
Stop until the tools are available.
0.3 — Fetch the issue
Call get_issue with the provided issue ID. If the issue does not exist, report the error and stop. If it exists, extract and display the fields listed in references/issue-fields.md. Keep the raw issue data available for later phases.
0.4 — IDEA MCP (MPS project)
Check that the mcp_idea_* tools are available.
If not available:
IDEA MCP is not connected. Please open the MPS project in IntelliJ IDEA with the MCP plugin running and retry.
What ships with it
8 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.
- 3d ago First seen · 135 lines · 87 tokens per session scan A 00e8baddab9f
mps-bugfix is a skill published in the GitHub repository JetBrains/MPS (1,657 stars, last pushed yesterday), licensed Apache-2.0. It adds 87 tokens to every session and 1,497 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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