What is fcp-drawio CLAUDE.md?

Project instructions for fcp-drawio, an MCP server that lets an AI create and edit draw.io diagrams through text operations. MCP is a standard way for an AI to call tools provided by another program.

They help navigate the parser, semantic model, layout, XML serialization, server, and component library, and specify how to build and test the TypeScript project.

They give agents the project’s architecture, important directories, implementation approach, and commands needed to work consistently.

How os-tack/fcp-drawio configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to os-tack/fcp-drawio. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/os-tack/fcp-drawio/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/os-tack/fcp-drawio

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/os-tack/fcp-drawio/claude-md/github.svg)](https://agentmods.dev/instructions/os-tack/fcp-drawio/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/os-tack/fcp-drawio/claude-md"><img src="https://agentmods.dev/badge/instructions/os-tack/fcp-drawio/claude-md/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/os-tack/fcp-drawio/claude-md"><img src="https://agentmods.dev/badge/instructions/os-tack/fcp-drawio/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 373 This file is loaded in full into every session.

When invoked 373 The same file — it is already loaded in full.

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

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	$0.00373	$0.00373
Opus 5.5	$0.00149	$0.00149
Sonnet 5.5	$0.00075	$0.00075
Haiku 4.5	$0.00037	$0.00037

Measured 2mo ago against content hash 272fc4807018, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

fcp-drawio CLAUDE.md 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 2mo 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.

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.

CLAUDE.md · 36 lines

What it actually says

fcp-drawio

Project Overview

MCP server that lets LLMs create/edit draw.io diagrams through intent-level operation strings. See docs/ for design documents and specifications.

Architecture

4-layer architecture:

MCP Server (Intent Layer) - src/server/ - Parses op strings, resolves refs, dispatches
Semantic Model (Domain Brain) - src/model/ - In-memory entity graph, event sourcing
Layout + Rendering - Part of model layer for Phase 1 (basic positioning)
Serialization - src/serialization/ - Semantic model ↔ mxGraphModel XML

Implementation Tier: Tier 3 (no native TypeScript SDK for draw.io). The DiagramModel semantic model + custom XML serializer is the correct pattern for this tier. See fcp-core/spec/implementation-guide.md.

Key Directories

src/types/ - Core TypeScript interfaces
src/model/ - Semantic model, event sourcing, reference registry
src/parser/ - Operation string parser
src/serialization/ - XML serialization/deserialization
src/server/ - MCP server, tools, intent layer
src/lib/ - Component library, themes, type resolver

Commands

npm run build - Compile TypeScript
npm test - Run tests (vitest)
npm run test:watch - Watch mode
npm run dev - Watch TypeScript compilation

Conventions

TypeScript strict mode
ESM modules (type: "module")
Tests co-located as *.test.ts files
vitest for testing
No maxGraph dependency - direct XML generation

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.

2mo ago First seen · 36 lines · 373 tokens per session scan A 272fc4807018

Subscribe to this mod's changes

fcp-drawio CLAUDE.md is an instructions file published in the GitHub repository os-tack/fcp-drawio (4 stars, last pushed 4mo ago), licensed MIT. It adds 373 tokens to every session, about $0.0015 per session on Opus 5.5. 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 2026-08-31.

Design and UX LLM diagrams drawio mcp model-context-protocol

fcp-drawio CLAUDE.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
fcp-drawio CLAUDE.mdos-tack/fcp-drawio	Instructions file	4	4mo ago	MIT	A	373	Claude Code
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vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	5,516	GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	274k	2d ago	MIT	A	4,313	Codex, OpenCode

fcp-drawio: Instructions file for Claude Code