Diagrams

Generates branded diagrams (cloud architectures with real provider icons, flowcharts, sequence and class diagrams, ER schemas, mindmaps, and Gantt charts) as high-resolution PNGs with automatic layout.

Animated enterprise AI platform architecture diagram on Google Cloud — Generated from: "Enterprise AI platform on Google Cloud", with real GCP icons, automatic layout, and animated export.

POST/api/v1/diagramsIncluded · Developer plan

Diagrams are a conversational resource: the response includes an opaque id that persists permanently (no expiry). Keep it to refine, restyle, export, or rename the same diagram any time.

POST

/api/v1/diagrams: create from a prompt → returns the image + a permanent diagram id.

POST

/api/v1/diagrams/:id/refine: with a prompt: follow-up content edits in plain English ("add a cache between the gateway and the DB"). Without one: a free, instant restyle (theme/size/transparent/nodeStyle/colors), no generation call spent, no wait.

GET

/api/v1/diagrams/:id: free regenerate/export: ?theme=, ?size=, ?transparent=1, ?format=png for raw bytes, ?format=svg for a standalone vector file (architecture diagrams only).

PATCH

/api/v1/diagrams/:id: rename only, no additional AI call, free. Pass { "title": "" } to clear the title.

No expiry: a diagram and its id live until you delete it or your account. Export the PNG any time; no need to "save" separately.

Parameters (create)

Field	Type	Description & options
prompt	Required	Describe the system, flow, schema, or plan in plain English. Up to 4000 characters.
type	String	What kind of diagram to draw. architecture = cloud/system topology with provider icons; er = entity-relationship. `architecture (default)flowchartsequenceclassermindmapgantt`
size	String	Canvas aspect ratio. Omit to use your account default (Authentication & concepts), else auto — the frame adapts to the diagram, vertical or landscape. The response reports the concrete size chosen. `auto (default)landscapeportraitsquarestory`
theme	String	Color mode. Omit to use your account default, else light. `light (default)dark`
style	String	Visual skin, architecture diagrams only. `glass (default)flatblueprinteditorial`
nodeStyle	String	Architecture only: structured = boxed pills, freeform = icon-only with no boxes. Omit to use your account default, else structured. `structured (default)freeform`
title	String	Optional fixed title; omit to let the engine write one.
transparent	Boolean	Generate with a transparent background (great for slides). Omit to use your account default, else false.
colors	Object	Palette override: { primary, secondary, background } hex values. Falls back to your brand colors.
brand	Object	Per-request brand override (name, logo, colors), to generate for a different brand without changing your saved profile. Persists on this diagram's refines too.
unbranded	Boolean	Brand mark. Diagrams are unbranded by default over the API/MCP — pass false to stamp your brand on this call, or turn it on for every call in Account → API & MCP defaults. See Authentication & concepts.

Refine accepts the same optional fields plus an optional prompt: present it for a content edit, omit it for a free restyle. Any omitted field keeps the diagram's current setting. Rename (PATCH) accepts only title. All three plus GET return the same shape: { id, type, title, size, theme, image, note? }, never the diagram's underlying source/structure — only the rendered image (PNG, or SVG via the vector export below).

Vector export (SVG)

GET /api/v1/diagrams/{id}?format=svg returns a standalone, self-contained image/svg+xml file — infinitely scalable, with real selectable and searchable text. Free, like every other re-render. Add &download=1 to save rather than open inline, and combine it with ?theme= / ?size= / ?transparent=1 as usual.

Architecture diagrams only. Other types return 400 svg_unsupported — ask for format=png instead.
Fonts travel with the file. Only the weights actually used are embedded, subsetted to the characters in your diagram — typically ~45KB total. Text renders identically on a machine that has none of the fonts installed.
Safe to inline several on one page. Gradient and filter ids are namespaced per file, so two diagrams in the same HTML document can't clash.
Renders faithfully in browsers, Inkscape and anything else honouring embedded @font-face. Design tools that map fonts by name (Figma, for instance) will substitute their own — the geometry is still exact, only the type differs.

Code sample: full loop

# 1) Create a diagram
curl -X POST https://api.capci.app/api/v1/diagrams \
  -H "x-api-key: capci_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Checkout flow: web app -> API gateway -> auth service -> payments service -> Postgres, async events to a queue",
    "type": "architecture",
    "size": "landscape",
    "theme": "dark",
    "brand": { "colors": { "primary": "#3b82f6" } }
  }'
# → { "id": "…", "type": "architecture", "title": "…", "size": "landscape", "theme": "dark", "image": "data:image/png;base64,…" }
# No expiry — the diagram and its id are permanent until you delete your account.

# 2) Refine it — keep the id, describe the change
curl -X POST https://api.capci.app/api/v1/diagrams/DIAGRAM_ID/refine \
  -H "x-api-key: capci_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{ "prompt": "add a cache between the API gateway and the payments service" }'

# 2b) Or restyle only — omit "prompt" entirely for a free, instant re-render
#     (no generation call spent, no wait)
curl -X POST https://api.capci.app/api/v1/diagrams/DIAGRAM_ID/refine \
  -H "x-api-key: capci_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{ "theme": "light", "nodeStyle": "freeform", "transparent": true }'

# 3) Rename it — no additional AI call, free
curl -X PATCH https://api.capci.app/api/v1/diagrams/DIAGRAM_ID \
  -H "x-api-key: capci_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{ "title": "Checkout flow v2" }'

# 4) Export the final PNG — free, any theme/size/transparency, no generation call
curl "https://api.capci.app/api/v1/diagrams/DIAGRAM_ID?theme=light&size=portrait&transparent=1&format=png" \
  -H "x-api-key: capci_your_api_key" -o diagram.png