Overview

What is This

A Cloudflare Worker that exposes an MCP (Model Context Protocol) server for plotting math functions, drawing STEM diagrams, and rendering the results as SVG or PNG. Source on GitHub: lingion/plot-mcp-worker.

Stack (verified against source)

Layer	What it does	Source
Runtime	Cloudflare Workers (ES module), compatibility date `2026-04-22`	`wrangler.toml`
Routing	JSON-RPC 2.0 at `POST /mcp`; web URLs at `/plot`, `/png`, `/s/{token}`, `/force.svg`, `/force-analysis.svg`, `/circuit.svg`, `/venn.svg`, `/c-memory.svg`, `/shape3d.html`, `/multi_plot`, `/multi_plot.png`	`src/index.ts` (handler at L3290)
Math engine	`expr-eval` parser for inline expressions like `sin(x)`, `x^2+1`	`src/plot.ts` (import L1)
SVG renderer	Hand-written string concatenation. Card layout, grid, ticks (nice/pi-aware/log), annotations, bar/box/pie/hist/scatter/line series	`src/render.ts` (1123 lines)
PNG renderer	`@resvg/resvg-wasm` compiled to WebAssembly; loads CJK font from KV and pathifies text	`src/render.ts` L1-3, L1073-1112
CJK font	`opentype.js` converts CJK glyphs and math unicode (π, ², ∫, √) to SVG paths so resvg can render them	`src/render.ts` L139-159 (`pathifyCjkText`)
Storage	Cloudflare KV namespace `SHORT_LINKS`; 30-day TTL on short link records; 8-char tokens	`src/constants.ts` L7-9; `wrangler.toml` L11-13
Diagram generators	Force analysis (8 templates), circuits (10 templates), Venn, C memory layout, 3D shapes	`src/extras.ts` (1657 lines); templates in `src/index.ts` L902-1173

Source tree

plot-mcp-worker/
|-- src/
|   |-- index.ts        3471 lines  HTTP entry + canonical tool dispatcher + short-link store
|   |-- render.ts       1123 lines  SVG/PNG rendering (math plots)
|   |-- plot.ts         1520 lines  PlotSpec builder, transforms, error bars, statistics
|   |-- extras.ts       1657 lines  Force/circuit/Venn/C-memory/3D SVG renderers
|   |-- types.ts        136 lines   Frozen interface (RenderFormat, PlotSeries, etc.)
|   |-- constants.ts    48 lines    Limits, palette, defaults
|   |-- router.ts       94 lines    Compat layer (legacy -&gt; canonical name)
|   |-- compat.ts       80 lines    Legacy name mapping table
|   |-- utils.ts        91 lines    Base64/gzip helpers, XML escape, clamp, parseInteger
|   |-- mcp.ts          26 lines    CORS headers + JSON-RPC 2.0 helpers
|   |-- types.d.ts      9 lines     Type declarations
|-- scripts/                       12 verification/deploy scripts (see Local Dev page)
|-- docs/                          README assets (CN/EN showcase images, examples)
|-- capabilities.json    Tool manifest (legacy format, 22 capabilities)
|-- wrangler.toml        Worker config (route, KV binding, .ttf rule)
|-- tsconfig.json        ES2022 strict, bundler resolution
|-- package.json         3 deps: expr-eval, opentype.js, @resvg/resvg-wasm

8,255 total source lines across 11 TypeScript files.

Two version numbers (intentional)

package.json: 0.2.0 — the npm/release version
src/constants.ts SERVER_VERSION: 0.4.14 — reported by health tool / initialize response

The mismatch exists because SERVER_VERSION tracks the deployed-worker iteration independently from the npm release. Don't try to align them — it's a deliberate separation between the deployment surface and the package surface.

Live MCP endpoint

POST JSON-RPC 2.0 to https://your-worker.your-domain.com/mcp. Initialize returns protocolVersion: "2025-03-26", server name plot-mcp-worker, version 0.4.14. Full tool list at /mcp tools/list returns 24 tools (see Tools Reference page).

See also: Technical post: Building plot-mcp-worker — deep dive into the expression parser, 5-transform data pipeline, smart axis intelligence, CJK text-to-path, and diagram generators.