AI agent skill · by @HoangNguyen0403

Common Architecture Diagramming

Draw architecture diagrams as editable draw.io files with a fixed house style, C4 levels, and evidence-tagged shapes. Use when producing a system context, container, deployment, data flow, sequence, or state diagram, or redrawing an ASCII or Mermaid one.

Archived 2026-10-23 · Source updated 2026-09-15 · License: MIT. Check the original repository for the latest version.

SKILL.md instructions

# Architecture Diagramming Standard

## **Priority: P1 (HIGH)**

## Pipeline

Never hand-write mxGraph XML. Write a spec; the scripts own every visual decision,
so diagrams stay identical across authors, repositories, and sessions.

1. Write `spec.json` — schema in [diagram-spec.md](references/diagram-spec.md). For an ERD,
   generate it: `python3 scripts/schema_to_spec.py db/schema.sql --title "<System> — ERD" -o spec.json`
2. `python3 scripts/validate_spec.py spec.json`
3. `python3 scripts/render_drawio.py spec.json -o docs/architecture/<slug>.drawio --strict`
   (exit 2 = a layout finding; change the spec, per [layout-rules.md](references/layout-rules.md))
4. Export the image: a draw.io MCP tool if the session has one, else
   `python3 scripts/export_drawio.py docs/architecture/<slug>.drawio -f png -o docs/architecture/<slug>.png`,
   else ship the `.drawio` and say the image was not exported. See [export paths](references/mermaid-fallback.md).

Commit the `.drawio` as the source of truth; the image is a copy for a deck.

## Guidelines

- **Name the audience and the decision** before drawing anything.
- **One C4 level per diagram**: context, container, or component, never mixed.
- **Pick the type from the message**, not from habit. See [diagram-selection.md](references/diagram-selection.md).
- **Evidence per node** as `path:line`. A node with no evidence renders dashed and
  marked UNVERIFIED — leave the flag showing rather than asserting a guess.
- **Put the number on the box.** `metric` carries the load or SLO that sized the node,
  `constraint` says why it exists; never invent either.
- **Label every edge** with its protocol or event; use `style: async` for events.
- **Cloud icons only where verified.** `gcp:*` and `aws:*` are official icons; every other
  vendor is a `cloud:*` kind with the service named in `sublabel`. No Azure logos exist in
  the bundle, so Azure is always `cloud:*`.
- **Exec audience caps at 12 nodes.** Past that, split by level or by flow.
- **Legend and title block are generated.** Do not remove or duplicate them.
- **Refine in draw.io, not in XML.** Re-running the renderer overwrites layout tweaks.

## Anti-Patterns

- **No hand-written XML**: Write the spec, run the renderer.
- **No invented boxes**: Omit what the evidence does not support.
- **No mixed levels**: Table columns never appear in a context diagram.
- **No unlabeled arrows**: State the protocol or the event.
- **No mystery acronyms**: Expand every abbreviation on first use.
- **No orphan nodes**: Connect it or cut it.

## Red Flags

| Thought | Reality |
|---------|---------|
| "It is one box, I will write the XML" | The renderer owns style, legend, and title block. Use it. |
| "Close enough, I will guess this service" | Guesses ship as facts. Omit the evidence and let it render UNVERIFIED. |
| "Managers want the whole system on one page" | Past 12 nodes they stop reading. Split it. |

## References

- [Diagram spec](references/diagram-spec.md) · [Style catalog](references/style-catalog.md) · [House style](references/house-style.md)
- [Source extraction](references/source-extraction.md) · [Exec readability](references/exec-readability.md)
- [C4 model](references/c4-model.md) · [Cloud](references/cloud-architecture.md) · [Best practices](references/best-practices.md)
- [Layout rules](references/layout-rules.md) · [Checklist](references/checklist.md) · [Export paths and Mermaid fallback](references/mermaid-fallback.md)
- Runnable examples: `assets/fixtures/<type>.spec.json`, one per diagram type, plus schema samples under `assets/fixtures/schemas/`.
- Batch or delegated drawing: `specialist-solution-diagrammer`.