Mep Settings Curation

mep-settings-curation

Revit hides the duct/pipe size catalogs and MEP system parameters inside Manage → MEP Settings. Schedules and the System Browser cannot reach them — they are setting definitions, not model elements, so the Revit API is the only path.

Four MCP tools cover this area. The method lives in domain/mep-mechanical-settings.md; that file wins on any conflict with this skill.

The one thing that matters most

Catalog ≠ usage. These are different questions and need different tools:

Deleting based on the catalog alone is blind deletion. The catalog does not know whether anything uses it.

Also: Used in Size Lists / Used in Sizing are not usage. They only control whether a size appears in dropdowns / participates in auto-sizing. A size with both unchecked can still have existing elements using it.

Tools

Procedure

Re-anchor first (repo CLAUDE.md rule): call get_project_info before anything else. One call at a time — the bridge holds a single-connection lock; concurrent calls wedge it with HTTP 409 (recover via the ribbon's 「切換/釋放連線」 button).

Phase 1 — Catalog inventory

get_mep_segments_and_sizes with summaryOnly: true first. A full dump runs to tens of thousands of characters and will blow the response limit; the summary gives every segment's size count and checkbox counts. Then drill with segmentName (e.g. "Copper - K") only where needed.

Use get_mep_settings when the question is about angles / slopes / fluids rather than sizes.

Phase 2 — Real usage

get_mep_size_usage. Scope it (scope, shape, segmentName) to what the user actually asked about.

Read three things out of the result:

• usageCount per catalog size — 0 means removable.
• orphans — sizes the model uses that the catalog lacks. These are add candidates, not errors.
• unattributedFittingSizes (pipe only) — fitting connectors carry a diameter but no segment, so they cannot be attributed. curate_mep_sizes blocks matching sizes by default.

Set includeElementIds: true when the user needs to know who is holding a size.

Phase 3 — Standards reconciliation

Compare the catalog against what the work requires. Read domain/mep-mechanical-settings.md §3 before making any claim about codes — it draws a line this phase depends on:

• Taiwan has no regulation for duct sizing friction rate or velocity limits. The only article naming duct velocity is 建築設備編 §106 (450 m/min), and it is a smoke-exhaust lower bound in m/min — the opposite direction and a different unit from supply-air sizing. Never present it as the value to type into the Sizing dialog.
• Real sizing values come from the design-manual layer (ASHRAE / SMACNA / SHASE / 公會), not from law. Carry their honesty markers: ✅ = primary source read, ⚠️ = second-hand. Never launder a ⚠️ value into a stated fact.
• Display units first. Sizing dialog units follow Project Units, so run set_project_units with mode='taiwan' before opening it — then metric design values can be typed directly.
• The catalog gates sizing. Auto-sizing can only pick sizes that are in the catalog and have Used in Sizing checked. Changing units alone does not give metric sizes; the catalog has to carry them.

Taiwan CNS specifics: §6.1 has the judgement (metal pipe A-呼稱 needs no change; PVC does). §6.2's discrete CNS size series is still missing — do not invent one. Note the distinction: continuous design values (friction/velocity) are sourced; the discrete size list is not. The add/remove protocol does not depend on it, so curation can proceed without it.

Phase 4 — Add / remove

curate_mep_sizes. Always dryRun: true first (it is the default) and show the plan to the user before executing.

• Add is unrestricted. One more option cannot break an existing element.
• Remove is guarded. The tool runs its own usage scan and blocks anything in use, reporting who is using it. Never argue past a block — either the user fixes those elements first, or that size stays.

The tool executes the four-step protocol internally: ① list → ② single Transaction → ③ QC by re-reading and diffing the catalog → ④ auto-restore anything accidentally removed. It always returns RestorePayload with the full definition of every removed size.

Read the Qc block back to the user. Qc.passed: false means something needs human attention — do not report success.

Parameters

get_mep_size_usage

curate_mep_sizes

Guardrails

• Never delete without Phase 2 in the same session. If the usage scan has not run this turn, run it.
• Never invent pipe inner/outer diameters. They drive hydraulic calculation. The tool rejects an add that omits them; ask the user for the real values instead of estimating.
• Do not tell the user to fix sizes through the dialog. Opening Segments and Sizes and pressing OK silently quantizes every inner diameter to the display precision (measured: Copper-K's true IDs 0.305" / 0.995" / 5.741" all snapped to 1/32" multiples). API writes do not do this — that is a reason to prefer the tool, and a reason to warn before the user opens that dialog on a model that matters.
• Angles are a separate risk class. Disabling a fitting angle can invalidate existing elbows. curate_mep_sizes deliberately does not touch angles; do not work around that.
• Report counts from tool output only (repo Tool-Call-Data-Honesty rule). Never state a size list or usage count from memory.

Reference

• domain/mep-mechanical-settings.md — the method: usage-scan sources, the four-step removal protocol, Revit API unit traps (angles are already degrees, slopes are percent, connector tolerance is an angle, duct inner/outer are placeholders), cross-version differences, and the Taiwan CNS judgement.
• set-project-units skill — display units, Taiwan §102 air flow.