Agent skill

generating-diagrams

Use when generating flowcharts, diagrams, dependency graphs, or visual representations of processes, relationships, architecture, or state machines. Triggers: 'diagram this', 'flowchart', 'visualize', 'dependency graph', 'ER diagram', 'state machine diagram', 'class diagram', 'sequence diagram', 'map the relationships', 'draw the architecture', 'how does X connect to Y'. NOT for: simple bullet point explanations, runtime monitoring, or text-only documentation.

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Install this agent skill to your Project

npx add-skill https://github.com/axiomantic/spellbook/tree/main/skills/generating-diagrams

SKILL.md

Generating Diagrams

Overview

Generate accurate, renderable, exhaustive diagrams from code, processes, instructions, or architecture. Every node justified by source material. Every reference traced to its deepest level. Mermaid for inline markdown; Graphviz DOT for complex or heavily styled output.

When to Use

  • Visualizing process flows, decision trees, or multi-phase workflows
  • Mapping dependency/invocation relationships between components
  • Documenting state machines or lifecycle transitions
  • Creating entity-relationship or class hierarchy diagrams
  • Analyzing skill, command, or instruction structure visually
  • Generating sequence diagrams for temporal interactions

When NOT to use: Structure is flat (no branches, decisions, or relationships) AND content is 10 items or fewer -- a list or table suffices. Runtime observability. Text-only documentation.

Invariant Principles

  1. Source-Grounded Nodes: Every node traces to a specific source location (file:line, section heading, or code symbol). No invented nodes.
  2. Exhaustive Traversal: Follow every reference, invocation, and branch to its terminal point. "..." and "etc." are forbidden. If too complex for one diagram, decompose into linked diagrams.
  3. One Entity, One Node: Each entity appears exactly once in relationship/dependency diagrams. Multiple connections use multiple edges, not duplicate nodes.
  4. Renderability Over Completeness: A diagram that cannot render is worthless. Always verify. When too complex for one diagram, decompose.

Quick Reference

Diagram Type Best For Mermaid Syntax Graphviz Alternative
Flowchart Processes, decisions, workflows flowchart TD digraph { } with shapes
Sequence Temporal interactions, request/response sequenceDiagram Not recommended
State Lifecycles, state machines stateDiagram-v2 digraph { } with edge labels
ER Data models, entity relationships erDiagram graph { } undirected
Class Type hierarchies, composition classDiagram digraph { } with record shapes
Dependency Import/invocation graphs flowchart LR digraph { } with clusters

Workflow

Phase 1: Analysis

Before generating any diagram, identify: subject type, traversal scope, source material locations, and rendering format.

1.1 Identify Diagram Subject

Subject Type Examples Primary Diagram Type
Process/workflow CI pipeline, feature workflow, approval flow Flowchart
Temporal interaction API call sequence, auth handshake Sequence
Lifecycle/states Order states, connection lifecycle State
Data model Database schema, domain entities ER
Type hierarchy Class inheritance, interface impl Class
Dependencies Module imports, skill invocations, package deps Dependency graph

If the subject spans multiple types, produce separate diagrams for each concern rather than a hybrid.

1.2 Scope the Traversal

Define boundaries BEFORE reading source material. Confirm with user; in autonomous mode, use default depth.

ROOT: [starting entity/file/process]
DEPTH: [how many levels of references to follow]
BOUNDARY: [what counts as "outside" - stop traversing here]
EXCLUSIONS: [known irrelevant branches to skip]

Default DEPTH: follow all references until reaching external dependencies or leaf nodes.

1.3 Select Format

Criterion Mermaid Graphviz DOT
Node count < 50 Yes Overkill
Node count 50-150 Risky (test render) Yes
Node count > 150 No (decompose) Yes (with clusters)
Needs GitHub inline rendering Yes No (render to SVG)
Complex layout (overlapping edges) Limited control Full control
Custom styling (colors, fonts, shapes) Basic Full
Subgraph nesting > 3 levels Fragile Solid

Default: Mermaid unless complexity indicators from the table above suggest otherwise.

1.4 Plan Decomposition (if needed)

When estimated node count exceeds format limits:

  1. Level 0 (Overview): High-level boxes with phase/component names. No internal detail. Include "see Diagram N" references.
  2. Level 1 (Phase Detail): One diagram per major phase/component. Shows all internal steps and decision points.
  3. Level 2 (Deep Dive): Optional. For phases that are themselves complex (e.g., a sub-skill with its own multi-phase workflow).

Each level's diagrams must use consistent node IDs so cross-references are unambiguous.

Phase 2: Content Extraction

2.1 Systematic Traversal Protocol

QUEUE = [ROOT]
VISITED = {}
NODES = []
EDGES = []

while QUEUE not empty:
    current = QUEUE.pop()
    if current in VISITED: continue
    VISITED.add(current)

    content = read(current.source_location)

    NODES.append({
        id: sanitize(current.name),
        label: current.display_name,
        source: current.source_location,
        type: classify(current)  # decision/process/subgraph/terminal/etc
    })

    for each reference in content:
        target = resolve(reference)
        EDGES.append({
            from: current.id,
            to: target.id,
            label: reference.context,
            condition: reference.condition or null
        })
        if target not in VISITED:
            QUEUE.append(target)

Extract from each source file/section:

  • Decision points (if/else, switch, routing logic)
  • Subagent dispatches or skill invocations
  • Data transformations (input -> output)
  • Quality gates (pass/fail with consequences)
  • Loop/retry logic
  • Terminal conditions (exit, error, completion)
  • Conditional branches (with the condition on the edge label)

2.2 Verify Completeness

  • Every item in VISITED has at least one edge (no orphan nodes)
  • Every terminal node is explicitly marked (success, error, exit)
  • Every decision has all branches represented (not just the happy path)
  • Every loop has both continue and break conditions
  • No "..." or placeholder nodes exist

Phase 3: Diagram Generation

3.1 Generate Diagram Code

Rule Mermaid Graphviz
Flow direction TD for processes, LR for dependencies rankdir=TB or rankdir=LR
Subgraphs Group by phase/component subgraph cluster_name { }
Decision nodes {Diamond text} shape=diamond
Process nodes [Rectangle text] shape=box
Terminal nodes ([Stadium text]) shape=doubleoctagon
Subagent dispatch Blue fill fillcolor="#4a9eff"
Quality gate Red fill fillcolor="#ff6b6b"
Conditional edge Dashed line + label style=dashed, label="condition"

Node label guidelines:

  • Max 5 words per line
  • Use <br/> for line breaks in Mermaid, \n in Graphviz
  • Put detail in edge labels or annotations, not node labels
  • Reference skill/command names inline: Invoke: skill-name

Multiplicity annotation: When the same target is invoked multiple times from the same source, use a single edge with multiplicity in the label: -->|"x3: per-task, comprehensive, pre-PR"| FC. Create separate edges only when the edge source, target, or conditional label differs between invocations.

3.2 Generate Legend

Every diagram MUST include a legend. For Mermaid, add a disconnected subgraph:

mermaid
subgraph Legend
    L1[Process Step]
    L2{Decision Point}
    L3([Terminal])
    L4[/Input-Output/]
end

Include color meanings if using classDef or fill colors. For Graphviz, add subgraph cluster_legend.

3.3 Generate Cross-Reference Table

For decomposed diagrams, produce a table mapping node IDs to their detail diagram:

Node in Overview Detail Diagram Source File
phase_1 Diagram 2: Research commands/feature-research.md
phase_2 Diagram 3: Design commands/feature-design.md

Phase 4: Verification

4.1 Syntax Check

  • Mermaid: Paste into mermaid.live or a local renderer
  • Graphviz: Run dot -Tsvg input.dot -o output.svg
  • If no renderer available, manual syntax audit:
    1. Count opening/closing braces and brackets (must match)
    2. Verify every subgraph has a matching end
    3. Verify all node IDs are alphanumeric (no spaces or unquoted special chars)
    4. Verify all edge labels use correct quoting (|"label"| for Mermaid)
    5. Verify classDef names match class references
    6. Check for Mermaid reserved words used as node IDs (end, graph, subgraph)

4.2 Renderability Check

Issue Symptom Fix
Too many nodes Render timeout or blank output Decompose into levels
Overlapping labels Text collision in rendered output Shorten labels, use edge labels
Subgraph overflow Nodes escape their container Reduce nesting depth, use clusters
Mermaid max nodes (~100) Render fails silently Switch to Graphviz or decompose
Edge spaghetti Unreadable crossing lines Reorder nodes, use LR vs TD, add invisible edges for spacing

4.3 Completeness Check

  • Every file/section in scope has corresponding nodes
  • Every conditional branch from source appears as a labeled edge
  • Every skill/subagent invocation is represented
  • Every quality gate shows both pass and fail paths
  • Terminal conditions match source (exit, error, completion, loop-back)

If anything is missing, return to Phase 2 and re-traverse.

After generating any diagram, verify: every node traces to source, no placeholders remain, legend is present, syntax renders cleanly, and completeness check passes.

Mermaid in Markdown Files

When writing mermaid diagrams inside markdown files, use <br> for newlines within node labels. Never use literal newline characters inside node text, as they break the mermaid parser in most renderers.

Mermaid Syntax Reference

mermaid
flowchart TD
    A[Process] --> B{Decision}
    B -->|Yes| C[Action]
    B -->|No| D[Other Action]
    C --> E([Terminal])

    subgraph Group Name
        F[Step 1] --> G[Step 2]
    end

    style A fill:#4a9eff,color:#fff
    classDef gate fill:#ff6b6b,color:#fff
    class B gate
mermaid
sequenceDiagram
    participant A as Client
    participant B as Server
    A->>B: Request
    B-->>A: Response
    alt Success
        A->>B: Confirm
    else Failure
        A->>B: Retry
    end
mermaid
stateDiagram-v2
    [*] --> Idle
    Idle --> Processing: start
    Processing --> Complete: success
    Processing --> Failed: error
    Failed --> Idle: retry
    Complete --> [*]
mermaid
erDiagram
    SKILL ||--o{ COMMAND : "invokes"
    SKILL {
        string name
        string description
    }
    COMMAND {
        string name
        string phase
    }

Graphviz DOT Reference

dot
digraph G {
    rankdir=TD;
    node [shape=box, style=filled, fillcolor="#f0f0f0"];

    start [label="Start", shape=oval];
    decision [label="Decision?", shape=diamond, fillcolor="#ff6b6b"];
    process [label="Process Step", fillcolor="#4a9eff", fontcolor=white];
    end_node [label="End", shape=doubleoctagon, fillcolor="#51cf66"];

    start -> decision;
    decision -> process [label="Yes"];
    decision -> end_node [label="No", style=dashed];
    process -> end_node;

    subgraph cluster_phase1 {
        label="Phase 1";
        style=filled;
        fillcolor="#f8f9fa";
        a1 -> a2 -> a3;
    }
}

Common Mistakes

Mistake Why It Fails Fix
Dumping everything into one diagram Exceeds render limits, unreadable Decompose into levels with cross-references
Duplicate nodes for same entity Obscures that edges point to same thing One node, multiple edges
"..." or "etc." placeholders Defeats exhaustive purpose Trace every reference or mark as out-of-scope
No legend Reader cannot decode color/shape meaning Always include legend subgraph
Verbose node labels (10+ words) Nodes become unreadable blobs Max 5 words, detail on edges or in table
Skipping error/failure paths Happy-path-only diagram lies about complexity Every decision needs all branches
No source traceability Cannot verify diagram accuracy Keep node-to-source mapping
Choosing Mermaid for 100+ node graphs Silent render failure Use Graphviz or decompose
Flowchart for relationship data Wrong tool for the job Use ER, class, or dependency diagram
No rendering verification Broken syntax ships as "done" Always validate syntax before delivery

Rationalization Counters

Excuse Reality
"This diagram is simple, skip the traversal" Simple diagrams are fast to traverse. Skipping risks missing edges. Always traverse.
"I'll add the legend later" Later never comes. Generate it with the diagram.
"Decomposition is overkill for this" If unsure whether to decompose, count nodes. Numbers decide, not feelings.
"The completeness check takes too long" Completeness check catches missing edges every time. 2 minutes to check vs. delivering wrong diagram.
"I know this domain well enough to skip reading" Source-grounded means reading, not remembering. Read or mark out-of-scope.

Update Mode (Default)

When updating existing diagrams (the default path), the system classifies source changes before deciding how to proceed:

Tier 1: STAMP (Non-Structural)

Changes that don't affect the workflow diagram are stamped as fresh without regeneration.

  • Adding/modifying XML tags (e.g., <BEHAVIORAL_MODE>, <ROLE>, <CRITICAL>)
  • Changing prose, descriptions, or explanations within existing steps
  • Fixing typos, rewording instructions
  • Adding/removing FORBIDDEN or REQUIRED items
  • Changing code examples within steps

Tier 2: PATCH (Surgical Update)

Small structural changes trigger targeted edits to the existing diagram rather than full regeneration.

  • Adding or removing a single step within an existing phase
  • Renaming a phase or step
  • Adding a new quality gate
  • Reordering 1-2 steps

When patching, preserve ALL existing diagram structure, styling, and layout. Only modify the specific nodes, edges, or subgraphs affected by the change.

Tier 3: REGENERATE (Full)

Major structural changes fall through to the full 4-phase generation workflow above.

  • Adding or removing entire phases
  • Major reorganization of step ordering
  • Changing flow/branching logic
  • Adding new parallel tracks or decision points

Invocation

  • generate_diagrams.py --interactive uses smart classification by default
  • generate_diagrams.py --force-regen bypasses classification for full regeneration
  • On any classification or patching error, falls back to full regeneration automatically

<FINAL_EMPHASIS> Every node traces to source. Every diagram renders. Every phase executes. Shortcuts produce wrong diagrams that mislead -- and a wrong diagram is worse than no diagram at all. </FINAL_EMPHASIS>

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