io.github.ganapativs/microcharts MCP Server

<div align="center"> <img src="assets/promo.png" alt="microcharts — word-sized charts for React, made for AI first and for the people reading what it writes. 106 chart types, zero dependencies, ~2–7 kB interactive · ~1–4 kB static." width="920">

@microcharts/react

Word-sized charts for React — zero runtime dependencies, ~2–7 kB interactive · ~1–4 kB static, accessible by default, and server-component safe.

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Docs · Gallery · Quickstart · AI usage · llms.txt

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microcharts is 106 tiny, handcrafted chart types built to sit inside an interface: a sentence, a table cell, a KPI card, a tab header, a streamed AI reply. The grammar is small enough for a model to emit correctly mid-sentence, and every chart describes itself in words, so a chart an LLM streams into a chat reply is one a person can read and check.

Status: tested and in production use, but not across every stack and edge yet. If you hit something, open an issue on GitHub.

Why

• AI-native. A chart is plain data plus a generated sentence. One grammar across all 106 types — a model that has seen one chart can write them all. → AI usage
• Zero dependencies. No chart engine, no D3 — just SVG. React is the only peer. CI-enforced, forever.
• Server-component safe. Static charts are hook-free and render to HTML with zero client JavaScript. Interactivity is a separate opt-in /interactive import.
• Accessible by default. Every chart is an img with a natural-language summary built from your data; it updates when the numbers do. → Accessibility
• Tiny. ~2–7 kB interactive · ~1–4 kB static gzip per chart, budget-gated in CI. Every type has one documented, honest encoding channel and a stated precision.
• Motion, opt-in. Interactive charts draw on with animate plus one import "@microcharts/react/motion", and glide continuous marks when data updates. Entrances respect prefers-reduced-motion and never replay over server-rendered HTML. → Motion

Install

npm install @microcharts/react

Import the stylesheet once at the root of your app — it carries every theming token and chart style in a low-specificity cascade layer, so your own styles always win:

// app/layout.tsx
import "@microcharts/react/styles.css";

Your first chart

Every chart renders from data alone. This works in a React Server Component with zero client JavaScript — pure SVG, and its accessible name is generated from the data.

import { Sparkline } from "@microcharts/react/sparkline";

<Sparkline data={[3, 5, 4, 8, 6, 9]} title="Weekly revenue" />;

Each chart imports from its own subpath, so you only ship what you use. Every chart follows the same two-entry pattern: a static default, and an /interactive twin.

Add interactivity

Need hover, keyboard navigation, touch, or live announcements? Import the same chart from /interactive. The rendered output and the accessible name are identical, because the interactive entry composes its static twin. It only adds props; you opt into the client component where it matters.

import { Sparkline } from "@microcharts/react/sparkline/interactive";

<Sparkline data={[3, 5, 4, 8, 6, 9]} title="Weekly revenue" />;

Every interactive chart shares one contract, so you learn it once. Hover or arrow keys make a unit active; a click, tap, <kbd>Enter</kbd>, or <kbd>Space</kbd> selects it and pins the readout so it survives blur; <kbd>Escape</kbd> or a press outside the chart clears; <kbd>Home</kbd>/<kbd>End</kbd> jump to the ends. Read it back with onActive and onSelect — payload { index, value, label?, formatted? }, where value is the raw number and formatted is the chart's ready-to-display string — and control the pin with selectedIndex / defaultSelectedIndex. Set readout={false} to hide the in-chart value chip and render datum.formatted wherever you like. Single-unit scalar charts (Delta, Progress, StatusDot, Bullet, …) take onSelect alone.

<Sparkline data={[3, 5, 4, 8, 6, 9]} onActive={(d) => setHovered(d?.value ?? null)} onSelect={(d) => pin(d)} />

Annotate with children

Thresholds, markers, and target zones are children — the same grammar on every chart that supports them:

import { Sparkline } from "@microcharts/react/sparkline";
import { Threshold, Marker } from "@microcharts/react/annotations";

<Sparkline data={[120, 180, 240, 210, 260]} title="Latency p95">
  <Threshold y={200} label="SLO" />
  <Marker x={2} celebrate />
</Sparkline>;

Theme it

About two dozen --mc-* CSS custom properties are the runtime contract; presets are token bundles. Set one on a subtree with the provider — presets are visual only and never change what the data means:

import { MicroProvider } from "@microcharts/react";

<MicroProvider theme="editorial">
  <Sparkline data={[3, 5, 4, 8, 6, 9]} />
</MicroProvider>;

Presets: modern (default), editorial, mono, vivid, plus output-context print and eink. Dark mode is hand-tuned, not inverted. For a whole brand theme, defineTheme (from @microcharts/react/theme) derives a matched, color-blind-safe palette and dark twins from one accent:

import { defineTheme } from "@microcharts/react/theme";

const brand = defineTheme({ accent: "#6d28d9" });
<MicroProvider style={brand.style}>…</MicroProvider>;

Retune density with one scalar (--mc-density), give figures their own face (--mc-font-numeric), or recolor a single categorical chart with a colors array. → Theming guide

The catalog

106 stable chart types — 34 core, 26 decision, 23 expressive, 23 frontier — grouped by the question each one answers. data alone always renders something correct, and a prop name means the same thing on every chart (domain, color, title, summary, label, format…), so picking a chart is picking the question you need answered.

Sparklines, bars, deltas, and bullets through bump charts, funnels, honeycombs, calendar strips, and confidence bands — browse them all in the live gallery →

Not shipping, on purpose: pie, needle-gauge/speedometer, battery, waffle, violin. Each fails at micro scale or on the honest-encoding bar, and each has an in-catalog replacement (Bullet for gauges, SegmentedBar for pie, MicroBox for violin). → what to use instead

Made for models

A model writes the chart; a person reads it. The docs site publishes machine surfaces alongside the human ones:

Surface	What it is
/llms.txt	Curated map of the catalog and guides
/llms-full.txt	The complete generated docs corpus
/catalog.json	Every chart's name, import path, props, data shapes

The MCP server

The surfaces above are for reading. @microcharts/mcp lets an assistant call the library directly: a Model Context Protocol server that runs on your machine over stdio, with three tools backed by this library — find the chart type that answers a question, get its exact props and a ready-to-render sample, and render it to a self-contained SVG with the generated alt text attached.

{
  "mcpServers": {
    "microcharts": {
      "command": "npx",
      "args": ["-y", "@microcharts/mcp"]
    }
  }
}

Works in Claude Desktop, Claude Code, Cursor, and VS Code; nothing is hosted and no key is involved. The same three capabilities ship as Vercel AI SDK tools on the @microcharts/mcp/ai-sdk subpath. Full reference: microcharts.dev/docs/mcp. Also listed in the Glama MCP registry.

Compatibility

React 18 and 19. ESM-only, per-component subpath exports, types-first export conditions. Static charts render in any RSC or SSR setup with no client runtime.

sideEffects is a two-entry allowlist, never false: styles.css and the opt-in ./motion engine are both imported for their side effects, and false would let a bundler drop them. Every other module is side-effect free and tree-shakes normally, and since charts ship as per-component subpaths, you only pay for the ones you import.

Contributing

pnpm install
pnpm check     # typecheck + lint + format + test + knip
pnpm size      # gzip budgets (needs a build first)
pnpm build

Bug fixes and fixes to existing charts are the most useful thing to send. New props and new chart types are open but held to a high bar — the catalog is already broad at 106 types, so a new one needs a question the others can't answer. Either way, open an issue and wait for a yes before you open a PR. CONTRIBUTING.md has the policy, the CI gates, and what a good bug report contains.

License

MIT © Ganapati V S