A skill for creating and checking Mermaid diagrams, which are text-based diagrams used in Markdown.

Making flowcharts, sequence diagrams, state diagrams, and database relationship diagrams, then validating them with the supplied script.

It provides guidance for choosing diagram types and checking their syntax, reducing errors in diagrams stored as text.

mermaid — Skill for Claude Code by bendrucker

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add bendrucker/claude --skill diagram

Clone the repo

git clone --depth 1 https://github.com/bendrucker/claude

Made for: Claude Code.

Or install mermaid, the plugin that ships this one along with the rest of its 1 skill.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/bendrucker/claude/diagram.svg)](https://agentmods.dev/skills/bendrucker/claude/diagram)

Your own site

<a href="https://agentmods.dev/skills/bendrucker/claude/diagram"><img src="https://agentmods.dev/badge/skills/bendrucker/claude/diagram.svg" alt="Measured on agentmods" height="20"></a>

Per session 23 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 310 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00023	$0.00310
Opus 5	$0.00012	$0.00155
Sonnet 5	$0.00005	$0.00062
Haiku 4.5	$0.00002	$0.00031

Measured 7d ago against content hash e3aa7db0de78, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

mermaid scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/validate.test.ts, scripts/validate.ts), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/mermaid/skills/diagram/SKILL.md · 41 lines

What it actually says

Mermaid Diagrams

Create and validate Mermaid diagrams with syntax checking.

Diagram Types

Type	Directive	Use For
Flowchart	`flowchart TB`	Process flows, decision trees, system architecture
Sequence	`sequenceDiagram`	API interactions, message passing, protocols
State	`stateDiagram-v2`	State machines, lifecycles, status transitions
ER	`erDiagram`	Database schemas, entity relationships

Validation

Validate mermaid syntax in markdown files:

bun ${CLAUDE_SKILL_DIR}/scripts/validate.ts <file.md>

References

Flowchart — Nodes, edges, subgraphs, layout direction
Sequence — Participants, messages, activations, loops
State — States, transitions, composite states
ER — Entities, relationships, cardinality

Best Practices

Keep labels concise—use full descriptions in surrounding prose
Use subgraphs to group related nodes visually
Order participants/nodes to minimize edge crossings
Prefer left-to-right (LR) for timelines, top-to-bottom (TB) for hierarchies

Files

What ships with it

10 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

7d ago First seen · 41 lines · 23 tokens per session scan A e3aa7db0de78

Subscribe to this mod's changes

mermaid is a skill published in the GitHub repository bendrucker/claude (16 stars, last pushed yesterday), licensed MIT. It adds 23 tokens to every session and 310 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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