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-node-editingnpx skills add JetBrains/MPS --skill mps-node-editinggit 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 | $0.00067 | $0.02010 |
| Opus 5 | $0.00034 | $0.01005 |
| Sonnet 5 | $0.00013 | $0.00402 |
| Haiku 4.5 | $0.00007 | $0.00201 |
Grade A, and why
mps-node-editing 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 — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MPS Node Editing
The core workflow for mutating MPS nodes through MCP tools. JSON blueprints describe the node hierarchy you want; the tools resolve concepts, references, and used languages on insert.
Critical Directives
- Always use the fully qualified concept name in the
conceptfield — it is unambiguous and does not require aconceptReference. - Resolve before editing — call
mps_mcp_get_current_editor_root_node(for the user's focus) ormps_mcp_search_root_node_by_name(by name) to lock onto the target. Don't guess refs. - Prefer surgical edits —
mps_mcp_update_node(ADD/CHILDorSET/CHILD) preserves persistent IDs.mps_mcp_update_root_node_from_jsonrewrites the entire root and is wasteful when only one subtree changed. - Don't delete-and-reinsert to make a small change — deletion destroys persistent IDs and breaks incoming references.
- Cloning an existing node? Use
mps_mcp_alter_nodesCOPY_NODE, not a JSON blueprint. It clones the subtree natively — correct concept, properties, refs, nested structure — as the next sibling (multi-child role) or new root, then tweak withmps_mcp_update_node. Reserve JSON blueprints for nodes with no close match to copy from. - Validate frequently — call
mps_mcp_check_root_node_problemsimmediately after inserting or modifying a complex node."ok": truefrom insert does not mean the AST is semantically valid.
mps_mcp_update_node — Unified Node-Mutation Tool
All child, property, and reference operations on existing nodes go through mps_mcp_update_node. The operation is selected via operation (ADD/SET/DELETE) × kind (CHILD/PROPERTY/REFERENCE).
| operation × kind | Required parameters | Notes |
|---|---|---|
ADD × CHILD |
nodeReference (parent), childRole, childJson |
Optional position (0-based; null/-1 = append) and dryRun. A position ≥ the current child count clamps to an append; a negative value other than -1 is rejected. The response's data.index reports the actual landing index. |
SET × CHILD |
childNodeRef, childJson |
Replaces an existing child; preserves its position in the role. Optional dryRun. |
DELETE × CHILD |
childNodeRef |
Removes the child from its parent. |
SET × PROPERTY |
properties = [[nodeRef, propertyName, value], …] |
Batch operation; returns per-row results. |
DELETE × PROPERTY |
nodeReference, propertyName |
Clears a single property. |
SET × REFERENCE |
references = [[nodeRef, role, targetRefOrName], …] |
Batch operation; targetRefOrName accepts an r:... ref or a plain name. A plain name is resolved within the reference role's search scope; if it cannot be resolved the call fails (NOT_FOUND), preserves the previous reference value, and stores no dangling reference. |
DELETE × REFERENCE |
nodeReference, referenceRole |
Clears a single reference. |
What ships with it
3 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 · 82 lines · 67 tokens per session scan A aa7fad571ec8
mps-node-editing is a skill published in the GitHub repository JetBrains/MPS (1,657 stars, last pushed today), licensed Apache-2.0. It adds 67 tokens to every session and 2,010 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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