mermaid-diagrams

mermaid-diagrams is a skill for Claude Code from diillson/chatcli. It costs 74 tokens per session (527 once invoked), scanned B, original, Apache-2.0.

A diagram-as-code tool that creates flowcharts, timelines, architecture diagrams, and other visuals from text using Mermaid.

In plain words
What is it for?
Documenting workflows, software architecture, database relationships, class structures, sequences, and project timelines.
Why use it?
Text-based diagrams can be edited, stored with code, and rendered into SVG or PNG files.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Documenting workflows, software architecture, database relationships, class structures, sequences, and project timelines.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/diillson/chatcli/mermaid-diagrams
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 diillson/chatcli --skill mermaid-diagrams
Clone the repo
git clone --depth 1 https://github.com/diillson/chatcli

Made for: Claude Code.

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.

agentmods badge for mermaid-diagrams

README.md
[![agentmods](https://agentmods.dev/badge/skills/diillson/chatcli/mermaid-diagrams/github.svg)](https://agentmods.dev/skills/diillson/chatcli/mermaid-diagrams)
Your own site
<a href="https://agentmods.dev/skills/diillson/chatcli/mermaid-diagrams"><img src="https://agentmods.dev/badge/skills/diillson/chatcli/mermaid-diagrams/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for mermaid-diagrams

Your own site · 80×15
<a href="https://agentmods.dev/skills/diillson/chatcli/mermaid-diagrams"><img src="https://agentmods.dev/badge/skills/diillson/chatcli/mermaid-diagrams.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 74 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 527 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Data Exfiltration · line 53
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00074 $0.00527
Opus 5 $0.00037 $0.00264
Sonnet 5 $0.00015 $0.00105
Haiku 4.5 $0.00007 $0.00053

Measured 6d ago against content hash 2b72f5ca6d00, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade B, and why

mermaid-diagrams scanned grade B with 2 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 6d ago.

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.

Sends data to an external URLmediumData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

curl -s -X POST https://kroki.io/mermaid/svg -d @diagram.mmd -o diagram.svg

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s -X POST https://kroki.io/mermaid/svg -d @diagram.mmd -o diagram.svg
pkg/persona/builtin/skills/mermaid-diagrams/SKILL.md · 63 lines

What it actually says

Mermaid Diagrams

Diagrams-as-code. Author Mermaid markup, then render it. Two render paths — prefer local, fall back to the keyless Kroki HTTP service.

1. Author the Mermaid

Write a .mmd file. Examples:

Flowchart:

flowchart TD
  A[Client] --> B{Auth?}
  B -- yes --> C[Serve]
  B -- no --> D[401]

Sequence:

sequenceDiagram
  User->>API: POST /login
  API-->>User: 200 + token

Mermaid also covers classDiagram, erDiagram, gantt, stateDiagram-v2, mindmap.

2. Render

Local (preferred)@mermaid-cli (mmdc):

mmdc -i diagram.mmd -o diagram.svg          # or -o diagram.png -t dark -b transparent

Detect: command -v mmdc / Get-Command mmdc. Install: npm i -g @mermaid-js/mermaid-cli.

Keyless service (no install) — Kroki:

curl -s -X POST https://kroki.io/mermaid/svg -d @diagram.mmd -o diagram.svg

(Use @webfetch/curl. For private content prefer local rendering — Kroki receives the source.)

Rules

  • Keep the diagram readable: group/label nodes, limit to what answers the question.
  • For chat/messaging contexts, you can also just send the fenced ```mermaid block as text — many clients render it. Render to an image when the user wants a file.
  • Report the output path after rendering.
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.

  1. 6d ago First seen · 63 lines · 74 tokens per session scan B 2b72f5ca6d00

Subscribe to this mod's changes

mermaid-diagrams is a skill published in the GitHub repository diillson/chatcli (90 stars, last pushed today), licensed Apache-2.0. It adds 74 tokens to every session and 527 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 2 findings (sends data to an external url, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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