Explain Drawing

Interpret a specific drawing element — a detail, section, callout, schedule reference, or sheet — in plain English. Output is an inline explanation with NCS-6 sheet/detail citation. For a full drawing-set walk-through, use the drawing-reader skill instead.

Input you need

Before interpreting, gather:

• Sheet identification — sheet number (NCS-6 format: A-301, S-201, M-401, E-501), sheet title (e.g., WALL SECTIONS, RCP — LEVEL 3), and discipline (A Architectural / S Structural / M Mechanical / P Plumbing / E Electrical / FP Fire Protection / C Civil / L Landscape / T Telecom).
• Drawing element — what specifically the user wants explained:
  • Detail callout — 4/A-301, Detail 6 / A5.21, SIM A-301/4.
  • Section cut — Section A-A on A-201, Building Section 1 on A-401.
  • Schedule reference — Door Type 12 / A-601, Window Type W-04 / A-602.
  • Plan callout — Room 305 — see RCP A-201, keynote 14 on A-101.
  • Title block / general notes — issue revision triangle, code analysis block, sheet index reference.
• Drawing content — the user must provide either:
  • A paste of the drawing text / callouts / dimensions / notes the question is about, OR
  • The PDF path so the drawing-reader skill or Read tool can pull the page.
  • Do not invent dimensions, materials, or callout numbers.
• Issue / phase — IFP (Issued for Permit) / IFC (Issued for Construction) / IFB (Issued for Bid) / 100% CD / Record Drawings / As-Built. Affects how the response treats binding-vs-informational content.
• Specific question — what the user wants to know. Examples: "What does keynote 14 reference?", "Is this a fire-rated assembly?", "What's the slab depression at the bathroom?", "Why is this section cut here?"

If any required input is missing, list the gap and stop. Do not interpret a drawing element without seeing its actual content.

Output structure

Produce a single Markdown response in this layout:

# Explain Drawing — [Sheet # / Element]

**Sheet:** [A-301 — Wall Sections]
**Discipline:** [Architectural / Structural / MEP / Civil / Landscape]
**Element:** [Detail 4/A-301 / Section A-A / Door Type 12 / etc.]
**Issue:** [IFP / IFC / IFB / 100% CD / Record / As-Built]
**Question:** [the user's specific question]

---

## What's drawn (literal description)

[2–4 sentences. The literal content of the element — geometry, materials shown, dimensions, callouts, hatching patterns. Quote callout text verbatim. Cite the specific detail / keynote / dimension as `(per Detail 4/A-301)` or `(keynote 14, A-101)`.]

## Plain-English meaning

[2–4 sentences. What this element communicates to the contractor / owner / consultant. If it's a coordination instruction, say so. If it's a representational convention (poché, hatching, line weight hierarchy), explain.]

## Cross-references

- [Bullet — other sheets / details this element points to. e.g., "Detail 4/A-301 references Spec Section 07 27 26 (air barrier) for membrane material."]
- [Bullet — schedules / specs this element depends on.]
- [Bullet — coordination items: "MEP penetration callout — confirm with M-401 RCP for fire-damper location."]

## NA AEC conventions used

- [Bullet — the NCS / AIA / industry conventions visible in this element. e.g., "SIM = `similar` per NCS-6 Module 02. Read with care; SIM details rarely match 1:1."]
- [Bullet — fire-rating annotation (`1HR`, `2HR`, `UL U419`), if visible.]
- [Bullet — dimension-string convention (face-of-stud / face-of-finish / centerline) if relevant.]

## Caveats

- This interpretation is based **only** on the drawing content the user provided. Cross-references that were not pulled may change the meaning.
- For binding interpretation on an `IFC` set, the AOR's RFI response governs — not this command. Open an RFI via `draft-rfi` if the drawing is ambiguous in the field.
- [Bullet — if `IFP`-only and not yet `IFC`, flag that contractor work cannot proceed off this set.]
- [Bullet — if `As-Built` / `Record`, flag that field conditions may differ from the drawing.]

NA AEC conventions (enforce)

• English only. No Hangul anywhere.
• Imperial-first units (ft, in, sf, °F, psf, plf); metric in parens only when useful. Do not lead with mm, m², °C.
• Sheet numbers use NCS-6 format: discipline letter + dash + sheet number (A-301, S-201, M-401, E-501, FP-101, C-201, L-101, T-301). Optional minor number (A4.1, A-301.01). Never "drawing 301" or "sheet 4-3" generically.
• Detail callouts use the NCS-6 numerator-over-denominator convention: 4/A-301 = Detail 4 on Sheet A-301. Treat SIM (similar) as a flag, not a guarantee — call it out per NCS-6 Module 02.
• Floor labels — Level 3, L3, or 3rd floor. Never 3F.
• Disciplines — A Architectural / S Structural / M Mechanical / P Plumbing / E Electrical / FP Fire Protection / C Civil / L Landscape / T Telecom. Use the actual NCS-6 letter, not a generic word.
• AIA / industry references — AIA G201 (Issuance), AIA G701 (Change Order), AIA A201 §3.7.4 (Contractor's responsibility for field conditions), AIA B101 §3.6.5 (Architect's response time).
• AHJs — name specifically (NYC DOB, LADBS, DSA, CA HCAI, NYC SCA, GSA, USACE) when the question involves a code-driven element. Never "the city" or "the AHJ" generically.
• Roles — Architect of Record (AOR), Engineer of Record (EOR), Owner, Owner's Representative, General Contractor (GC), Construction Manager (CM). Never "Director" as a project role.

Constraints

• Do not invent dimensions, materials, callout numbers, schedule entries, or keynote text. If the user did not paste the content, route through drawing-reader skill or Read tool first.
• Do not invent NCS-6 sheet numbers. Cite only what appears in the user's input.
• Distinguish literal description (what's drawn) from interpretation (what it means). Keep them in separate sections — the literal description is just the drawing content; the interpretation is the architectural intent.
• This command coexists with the drawing-reader skill. If the user wants a multi-element walk-through or a sheet-index summary, redirect to drawing-reader rather than padding this command's output.
• For schedule-heavy questions (door, window, finish, equipment schedules), suggest the schedule-extractor skill — pulling the whole schedule is its job, not this command's.
• Markdown only. This is an inline interpretation, not a transmittal document — no Word / PDF output and no aec-doc-gen dependency.

Workflow

1. Echo back what was parsed: sheet #, discipline, element type, issue, question. One line.
2. If the drawing content is missing, list the gap and stop. Suggest drawing-reader skill or Read tool as the retrieval path.
3. If the issue / phase is missing on a binding question (IFC vs. IFP changes how to answer), ask before interpreting.
4. Produce the full Markdown response in one shot.
5. After the response, list any cross-referenced sheets / specs / schedules the user should pull next (e.g., "If you want the membrane spec, pull Section 07 27 26 — use explain-spec or arch-rag").