diagrammer

Diagrammer authoring guide

You are producing a single JSON document that the Diagrammer viewer will render on a pannable, zoomable canvas. Do not output prose around the JSON unless the user explicitly asks for it; emit one fenced JSON block.

Output contract

• Top-level keys: version, type, title, nodes, edges. Optional: description, meta.
• version MUST be the string "1".
• type MUST be one of: mindmap, tree, flowchart, graph, concept, timeline. Pick the type that matches the user's intent — see the guidance below.
• nodes[*].id must be unique, stable, and URL-safe (^[a-zA-Z0-9_-]+$).
• edges[*].from and edges[*].to must reference existing node ids.
• You may include x / y (in pixels, node-center coordinates) when the user wants a hand-tuned layout. Otherwise omit them and let the viewer compute positions per type. Manual edits in the viewer's edit mode write these coordinates back when the user moves nodes.
• Never place two nodes so their bounding boxes overlap or touch. When emitting x / y, leave at least ~16 px of clear space between every pair of node rectangles (treat label width × node height as the box). Nodes are 120–280 px wide and ~44–140 px tall depending on label/description length — budget for the wider end. The viewer auto-separates loaded maps as a safety net, but author with proper spacing so labels and edge handles don't crowd.

Choosing a type

Type	When to use
mindmap	Brainstorming, branches radiating from a single central topic.
tree	Strict hierarchy with one parent per child (org chart, taxonomy).
flowchart	Process or decision flow with directed steps.
graph	Arbitrary network: dependencies, relationships, citations, ER diagrams.
concept	Concept map with labelled, often bidirectional, links.
timeline	Linear sequence of events or milestones.

If the user is ambiguous, ask one clarifying question — or default to mindmap for "brainstorm" / "outline" intents, and flowchart for "process" / "how does X work" intents.

Node fields

{
  id: string                  // unique, stable, URL-safe
  label: string               // short, ideally <= 40 chars
  description?: string        // single-line subtitle, <= 80 chars
  shape?:    'rectangle' | 'rounded' | 'ellipse' | 'diamond' | 'hexagon' | 'pill'
  color?:    'default' | 'slate' | 'blue' | 'green' | 'amber' | 'rose' | 'violet' | 'cyan'
  emphasis?: 'normal' | 'strong' | 'subtle'
  parent?:   string           // hint for tree/mindmap hierarchy
}

Markdown formatting

Labels, descriptions, edge labels, and the map title render a small subset of inline markdown. Use it to add typographic emphasis or to mark up identifiers — not as decoration.

Syntax	Renders as
**bold**	bold text
*italic*	italic
_italic_	italic
`code`	inline monospace, e.g. for identifiers
~~strike~~	strikethrough
[text](url)	link (opens in a new tab)

Nesting is allowed (** `code` **). Markup that doesn't match these delimiters renders literally — no headings, lists, paragraphs, or HTML. Avoid links inside node labels; put them in description instead.

Visual conventions (use sparingly)

• emphasis: "strong" on the central node of a mindmap or the root of a tree.
• shape: "diamond" for decisions/branches in flowcharts.
• shape: "pill" for terminal/IO nodes (start, end, external service).
• color: "rose" for failure / error / risk nodes; color: "green" for success; color: "amber" for warnings or caveats. Use color to convey meaning, not decoration.
• Leave most nodes at shape: "rounded" and color: "default". Restraint reads as design.

Edge fields

{
  from: string                // node id
  to:   string                // node id
  label?:     string          // edge label, e.g. "yes", "no", "depends on"
  style?:     'solid' | 'dashed' | 'dotted'
  direction?: 'forward' | 'backward' | 'both' | 'none'
}

• Default direction is forward (single arrow at to).
• Use dashed for weak / conditional / async links; dotted for very weak or implied relationships.

Sizing guidance

• 5–25 nodes per map is the sweet spot. Past 30, the viewer remains usable but comprehension drops. Split into multiple maps if the user's request implies more.
• Keep labels concise. Move detail into description. Move long explanations out of the map entirely.
• Avoid cycles in tree and flowchart. Use graph or concept if cycles are essential.

Multiple groups in one map

A single map can contain multiple disconnected sub-diagrams that share the canvas without being linked. The viewer detects connected components automatically (via edges + parent hints) and lays each out independently, packing them side-by-side with padding. No special syntax is required:

• Just emit the nodes and edges for each group. Anything that has no edge or parent link to another group becomes its own cluster.
• The same type is applied to every component (e.g. all clusters use mindmap layout if type: "mindmap").
• Use this when the user asks to compare/show several small diagrams together, or to lay out parallel sub-trees, parallel flows, sibling ER schemas, etc.

Use meta.tags or per-node description to explain what each group represents — there is no dedicated group field.

Edge marker (line / arrow / double / back)

The direction field controls the arrowheads on the edge — i.e. the visual marker between the two endpoints:

direction	Marker	When to use
"none"	line —	Symmetric / undirected association.
"forward"	arrow →	Directed link from from to to (default).
"both"	double ↔	Bidirectional / mutual relationship.
"backward"	back arrow ←	Reversed direction (rare; usually re-order ends).

Default is "forward". Pick "none" for ER associations or concept-map links that have no inherent direction; "both" for ER many-to-many relationships, mutual dependencies, or symmetric concept-map links.

ER diagrams (entity–relationship)

ER diagrams are authored with type: "graph". The schema has no dedicated attribute list, but the existing fields cover the common case:

• Entity → one node per table/entity. Set shape: "rectangle" and label: "**EntityName**" (bold). Use description to list the attributes inline, comma-separated, with (PK) / (FK) markers — keep it under ~80 chars; if the entity is wide, split it into two lines via multiple short attributes or move secondary fields out of the diagram.
• Weak entity / lookup → color: "slate" and/or emphasis: "subtle".
• Primary domain entity → color: "blue" or emphasis: "strong".
• Relationship → an edge between the two entities. Put the verb plus cardinality in label, e.g. "places (1—N)", "has (1—1)", "tagged with (M—N)". Use direction: "both" when the relationship is not directional (most ER links).
• Chen-style explicit relationship node (optional, only when the relationship itself carries attributes): add an intermediate node with shape: "diamond" and edges entityA → relNode → entityB, each edge labelled with its side's cardinality (1, N, M).
• Cardinality notation: pick one and stay consistent. Recommended: 1—1, 1—N, M—N. Also acceptable: 1..1, 0..N, 1..*.

ER worked example

{
  "version": "1",
  "type": "graph",
  "title": "Order management ER",
  "description": "Customers, orders, line items, products.",
  "nodes": [
    {
      "id": "customer",
      "label": "**Customer**",
      "description": "id (PK), email, name, created_at",
      "shape": "rectangle",
      "color": "blue",
      "emphasis": "strong"
    },
    {
      "id": "order",
      "label": "**Order**",
      "description": "id (PK), customer_id (FK), placed_at, status",
      "shape": "rectangle",
      "color": "blue"
    },
    {
      "id": "line_item",
      "label": "**LineItem**",
      "description": "id (PK), order_id (FK), product_id (FK), qty, unit_price",
      "shape": "rectangle"
    },
    {
      "id": "product",
      "label": "**Product**",
      "description": "id (PK), sku, name, price",
      "shape": "rectangle",
      "color": "green"
    },
    {
      "id": "category",
      "label": "**Category**",
      "description": "id (PK), name",
      "shape": "rectangle",
      "color": "slate",
      "emphasis": "subtle"
    }
  ],
  "edges": [
    { "from": "customer", "to": "order",     "label": "places (1—N)",      "direction": "both" },
    { "from": "order",    "to": "line_item", "label": "contains (1—N)",    "direction": "both" },
    { "from": "product",  "to": "line_item", "label": "appears in (1—N)",  "direction": "both" },
    { "from": "category", "to": "product",   "label": "groups (1—N)",      "direction": "both" }
  ]
}

Worked example

{
  "version": "1",
  "type": "flowchart",
  "title": "Password reset flow",
  "description": "Happy path and failure branches.",
  "nodes": [
    { "id": "start",   "label": "User clicks 'Forgot password'", "shape": "pill" },
    { "id": "form",    "label": "Email entry", "shape": "rounded" },
    { "id": "lookup",  "label": "User exists?", "shape": "diamond", "color": "amber" },
    { "id": "send",    "label": "Send reset email", "shape": "rounded", "color": "blue" },
    { "id": "ack",     "label": "Generic ack screen", "shape": "rounded" },
    { "id": "click",   "label": "User clicks token", "shape": "rounded" },
    { "id": "valid",   "label": "Token valid?", "shape": "diamond", "color": "amber" },
    { "id": "set",     "label": "Set new password", "shape": "rounded", "color": "green" },
    { "id": "expired", "label": "Show expired notice", "shape": "rounded", "color": "rose" },
    { "id": "done",    "label": "Done", "shape": "pill", "color": "green", "emphasis": "strong" }
  ],
  "edges": [
    { "from": "start",   "to": "form" },
    { "from": "form",    "to": "lookup" },
    { "from": "lookup",  "to": "send",    "label": "yes" },
    { "from": "lookup",  "to": "ack",     "label": "no",  "style": "dashed" },
    { "from": "send",    "to": "ack" },
    { "from": "ack",     "to": "click" },
    { "from": "click",   "to": "valid" },
    { "from": "valid",   "to": "set",     "label": "yes" },
    { "from": "valid",   "to": "expired", "label": "no",  "style": "dashed" },
    { "from": "set",     "to": "done" }
  ]
}

Anti-patterns

• Do not include id collisions, dangling edges, or unreferenced isolated nodes (unless the user's request explicitly calls for them).
• Do not repeat the same idea under multiple ids — collapse synonyms.
• Do not invent layout coordinates by guessing pixel positions; let the viewer compute them unless the user explicitly asks for a custom layout (e.g. by editing in the viewer first).
• Do not emit overlapping x / y placements. If two nodes share or nearly share coordinates, drop the coords on both and let auto-layout space them.
• Do not include emoji in labels.
• Do not wrap the JSON in additional commentary unless asked. The user will paste the JSON directly into the viewer.