Beauty Diagram skill

Beauty Diagram beautifies Mermaid / PlantUML diagrams into

sleek, modern SVG or PNG. It runs as a public API; this skill

delegates to the bd CLI (npm package @beauty-diagram/cli) so you

keep zero state in the agent. (draw.io / SVG import is editor-only —

not exposed through /v1/*.)

When to use

• The user asks for a polished, professional, slide-ready version of a

diagram source they already have or you can generate.

• The user wants you to render Mermaid or PlantUML from a model-generated

source string.

• The user wants the server to generate a diagram from a text description

("draw me a signup flow", "diagram our deploy pipeline") — use

bd ai generate for this; it returns Mermaid source you then beautify.

• The user wants to share a diagram link (e.g. paste into Slack / a doc).
• The user has Mermaid in a repo (README, ADR, RFC) and wants to **export

SVGs** alongside.

• The user has a directory full of diagram source files and wants every one

of them rendered (e.g. "render all the .mmd files in docs/diagrams"). Use

bd batch.

• The user wants their **Markdown files (README, ADR, blog post) to display the

diagrams inline** on GitHub / their static site, not just show the source

code block. Use bd extract — three modes available:

• Default (inline): no flags. Injects /v1/beautify.svg?source=... URLs

after each fence. No API calls during extract, no files written, no quota

consumed. Always watermarked (anonymous endpoint).

• Share (--share): mints a /v1/share/.svg URL per unique fence.

Watermark-free for Pro/Premium. Requires an API key. Each unique

source consumes 1 share quota the first time; identical fences are

deduplicated; per-owner local cache means re-runs cost zero quota.

• Sidecar (--assets-dir ./img): writes local SVG files via /v1/export.

Watermark-free for Pro/Premium, consumes export quota.

GitHub strips raw inline , so any of these modes' ![](...)

reference is the correct embed strategy.

When NOT to use

• The user only wants the Mermaid source itself, not an export.
• The user wants pixel-precise control over the SVG markup (Beauty Diagram

rewrites layout for presentation; it does not preserve raw Mermaid output).

• The user wants the AI to "change the colors / theme / font / layout" of an

existing diagram. bd ai generate only does text → diagram; visual

styling is controlled by --theme on bd beautify, not by the AI.

• The user is in an offline environment with no network and no CLI install.

Required tool

The bd binary from @beauty-diagram/cli:

npx @beauty-diagram/cli help
# or, after install:
bd help

If the user has not installed it, prefer npx over a global install — it

respects their package manager and avoids polluting PATH.

Workflow

1. Identify or generate the source diagram.
• If the user has a .mmd / .puml file, use it.
• If the user describes the diagram in words and is on a paid plan, use

bd ai generate "" --out .mmd — the server returns

Mermaid source, which you can then beautify. Always write the source

to a file so the user can edit it; the first AI draft rarely lands.

• If the user describes the diagram and is not on a paid plan (or

prefers not to pay), write Mermaid source yourself (you are good at

this), save it to a file, then beautify.

• draw.io and free-form SVG imports are not accepted by /v1/*. If

the user has those, ask them to convert via the web editor first.

1. Decide on output type.
• Need an SVG file: bd beautify --out .svg
• Need a download URL or to track quota: bd export --out .svg
• Need a shareable link: bd share --title "..."

1. Run the command. Always write to a file (--out) rather than letting

the SVG flood the terminal / chat. AI generation can also pipe directly

into beautify: bd ai generate "..." | bd beautify - --out flow.svg.

1. Verify the result exists before reporting success. If the command

failed, surface the error code (e.g. quota_exhausted, not_authenticated,

parse_failed, prompt_injection) — those are actionable for the user.

1. Preserve the source. Never replace the original Mermaid / PlantUML file

with the generated SVG — keep them side by side. For AI-generated diagrams,

keep the .mmd file too: it is the editable artifact, the SVG is not.

Auth

• Demo (anonymous): zero setup. Watermarked SVG/PNG. Limits per IP:

20 /v1/beautify requests / minute, 1 /v1/export per 24h (trial

budget — enough for an agent to verify the toolchain end-to-end before

registering). /v1/share, /v1/usage, and **bd ai generate always

require auth** — anonymous AI calls are rejected before any model

invocation.

• Authenticated: the user runs bd auth login once with a key from

/account/api-keys.

Required for bd share, bd ai generate, unwatermarked output, and

repeated exports. bd ai generate additionally requires a Pro or

Premium plan and an API key with the ai:write scope.

If the user hits a not_authenticated, plan_not_allowed, or

quota_exhausted error, point them at /account/api-keys (PAT creation)

or pricing — don't silently retry. Anonymous error bodies include a

hints block with absolute signUpUrl / signInUrl / apiDocsUrl,

which is the canonical place to surface to the user.

Themes & tiers

--theme selects the visual style. Theme tier is enforced on **all bd

commands that hit a /v1/ endpoint with a PAT* — this includes

bd beautify, bd export, bd share, bd embed-url --share,

bd batch, bd extract --share, and sidecar mode of bd extract. If the request includes a

PAT and specifies a theme above that token's plan tier, the server returns

HTTP 403 theme_tier_required.

The only path that bypasses the tier check is the anonymous fallback

(no token, or the GET /v1/beautify.svg inline embed endpoint). Anonymous

callers may request any theme, but always receive watermarked output — there

is no tier-free, watermark-free path.

When the user's plan is unknown, default to modern (Free, broadly

slide-friendly). Run bd themes to introspect what the current token

can use — locked themes are marked with ✗. Premium signature themes

(blueprint, memphis) are subscriber-only and cannot be unlocked

with credit packs.

Animations are not currently selectable via the CLI — animation choice

is a web-editor concept; CLI export paths ignore animation.

Source-level directives

Instead of (or in addition to) CLI flags, you can embed bd: directives at

the very top of the source file. Both the bd CLI and the Obsidian plugin

parse them; the API server ignores them as native comments (graceful

degradation — the source still renders, just without the directive).

Mermaid — use %% comment syntax:

%% bd:theme=classic
%% bd:bg=transparent
flowchart LR
  A --> B

PlantUML — use ' comment syntax:

' bd:theme=classic
' bd:bg=transparent
@startuml
A -> B
@enduml

Supported keys:

Multiple directives stack, one per line. Blank lines between directives are

tolerated. The first non-directive non-blank line ends the directive block.

Override priority: CLI flag > source directive > server default.

When generating source for the user, prefer directives over CLI flags when:

• The source file will be re-used (Obsidian vault, shared repo) — the

directive travels with the file.

• The user asks for a "memphis theme" diagram without CLI context (write

%% bd:theme=memphis at the top of the .mmd file).

Directives are stripped before the source reaches the renderer — they do not

appear in the SVG output.

Commands cheat sheet

# Render a Mermaid file
bd beautify docs/architecture.mmd --theme modern --out docs/architecture.svg

# Same but treat output as a downloadable export (consumes export quota)
bd export docs/architecture.mmd --out docs/architecture.svg

# PNG export. --quality standard works for everyone; high needs pro, max needs premium.
# Higher tiers than the plan cap are silently clamped (X-BD-Scale-Clamped).
bd export docs/architecture.mmd --format png --quality high --out docs/architecture.png

# PlantUML works the same way; .puml / .plantuml / .pu auto-detected,
# otherwise pass --source-format plantuml.
bd export docs/architecture.puml --out docs/architecture.svg

# Create a public share link (returns absolute https://www.beauty-diagram.com/s/... URL)
bd share docs/architecture.mmd --title "Service architecture"
# → prints the URL on stdout

# Get an embeddable <img>-friendly URL for a diagram source.
# Default: anonymous inline URL (always watermarked) + a hint about --share.
bd embed-url docs/architecture.mmd --theme atlas
# One-shot saved share embed (clean output for pro/premium owners).
# Saves the diagram via /v1/share AND prints the embed URL in one step.
bd embed-url docs/architecture.mmd --share
# → prints https://api.beauty-diagram.com/v1/share/<token>.svg

# AI: generate a diagram from a text prompt. Output is Mermaid source —
# always write to a file so the user can iterate. Paid-only.
bd ai generate "user signup with email verification" --out docs/signup.mmd

# Optional shape hint when the prompt is ambiguous about diagram type.
bd ai generate "request lifecycle" --hint sequence --out docs/lifecycle.mmd

# One-shot pipeline: prompt → mermaid → beautify → SVG.
bd ai generate "deploy flow" | bd beautify - --out docs/deploy.svg

# Check remaining AI / export quota before kicking off a batch.
bd usage

# Render every diagram file under a directory in parallel.
# Recurses for .mmd / .puml / .plantuml / .pu; one /v1/export per file.
# Default concurrency=4, default failure mode is continue-on-error.
bd batch ./docs/diagrams --out-dir ./docs/svg --theme modern

# Same idea but for a glob (quote it so the shell doesn't expand first).
bd batch "src/**/*.mmd" --format png --concurrency 8

# Default: inline embed URLs (no files written, anonymous-watermarked, 5 KB/block cap).
# No API calls during extract — source encoded in the URL; browser fetches on demand.
bd extract README.md

# Share mode: mint /v1/share/<token>.svg per fence. Watermark-free for Pro/Premium.
# 1 share quota per unique source (cached locally; re-runs free). No 5 KB cap.
# Requires API key. Default keeps existing share tokens across re-runs;
# use --re-mint to force fresh tokens (e.g. collaborator taking ownership).
bd extract README.md --share
bd extract README.md --share --re-mint

# Sidecar mode: writes local SVG files via /v1/export.
# Pro/Premium plans get watermark-free output; consumes export quota.
bd extract docs/*.md --assets-dir ./img --concurrency 4

# Preview what bd extract would change without writing.
bd extract README.md --dry-run

Privacy

The API does NOT persist source unless the user calls bd share. Do not warn

about server-side storage when running beautify, export, or

ai generate — that is misleading. AI prompts are logged in hashed form

for abuse / quality monitoring; the raw text is not retained.

Anti-patterns

• ❌ Do NOT output a hand-crafted as a Markdown code block when

a Mermaid source exists. Always run Beauty Diagram and reference the file.

• ❌ Do NOT dump the raw SVG into the chat. Use --out and reference

the file path.

• ❌ Do NOT install Beauty Diagram engine code locally — the CLI is a thin

client; the engine lives behind the public API.

• ❌ Do NOT call bd ai generate to "tweak" an existing diagram (change

colors, theme, labels, layout). It is a fresh-generation tool only.

For visual tweaks, change --theme or edit the .mmd source by hand.

• ❌ Do NOT call bd ai generate speculatively — each call costs the user

monthly AI quota. Confirm the user wants AI generation before running it.

• ❌ Do NOT capture the SVG output of bd ai generate — the command outputs

Mermaid source on stdout, not SVG. Pipe into bd beautify - to render.

• ❌ Do NOT loop bd export N times in a shell for loop when the user has

many files. Use bd batch