flint-chart-author

flint-chart-author is a skill for Claude Code, Codex from microsoft/flint-chart. It costs 81 tokens per session (7,585 once invoked), scanned A, original, MIT.

A skill for creating chart specifications with flint-chart, a JavaScript charting library. It maps data fields to visual elements and can prepare charts for supported rendering systems.

In plain words
What is it for?
Use it to author, transform, validate, or render charts, including filtering, grouping, joining, pivoting, and reshaping data before chart creation.
Why use it?
It helps turn a table of data into a structured chart definition while keeping data preparation separate from chart styling.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/microsoft/flint-chart/flint-chart-author
Any agent
npx skills add microsoft/flint-chart --skill flint-chart-author
Clone the repo
git clone --depth 1 https://github.com/microsoft/flint-chart

Made for: Claude Code, Codex.

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 flint-chart-author

README.md
[![agentmods](https://agentmods.dev/badge/skills/microsoft/flint-chart/flint-chart-author.svg)](https://agentmods.dev/skills/microsoft/flint-chart/flint-chart-author)
Your own site
<a href="https://agentmods.dev/skills/microsoft/flint-chart/flint-chart-author"><img src="https://agentmods.dev/badge/skills/microsoft/flint-chart/flint-chart-author.svg" alt="Measured on agentmods" height="20"></a>
Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,585 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00081 $0.07585
Opus 5 $0.00041 $0.03793
Sonnet 5 $0.00016 $0.01517
Haiku 4.5 $0.00008 $0.00758

Measured 4d ago against content hash 032a2735c683, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

flint-chart-author 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 4d 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.

.github/extensions/flint-chart/skills/flint-chart-author/SKILL.md · 571 lines

How it starts

The opening of the file, as written. The whole thing — 571 lines — stays where its author put it; the contents beside it link to each section on GitHub.

flint-chart: authoring and using a chart spec

What you produce (and what you do NOT)

Your output is the spec: the chart_spec and semantic_types of a ChartAssemblyInput. You reference data columns by name. The host passes the resulting input to assembleVegaLite, assembleECharts, or assembleChartjs to get a backend spec.

You write the input spec, not the output spec. And critically:

  • DO emit chart_spec (chart type, channel→field mapping, properties) and semantic_types (field → semantic type).
  • Reference columns by name. How data itself gets bound depends on the situation — a URL, a host-side variable, or embedded rows (see "How data gets bound"). Embedding is fine for small tables; just don't re-serialize a large dataset by hand, since that risks truncation and silent value corruption and wastes tokens.
  • Transform data before Flint. If the requested chart needs aggregation, filtering, joins, pivots, derived columns, or long/wide reshaping beyond Flint's built-in static-series fold, use a coding, notebook, SQL, or data tool first. Then author the Flint spec against the transformed table.
  • Style after Flint, only when needed. Author structure in Flint. For a presentation tweak Flint does not express (a reference line, annotation, or shaded band), use the Vega-Lite escape hatch — see "Post-Flint style customization". Never feed edited Vega-Lite JSON back to render_chart.

When the user wants more than a spec

First decide which workflow the user is asking for:

  • Spec authoring only: return a ChartAssemblyInput or its semantic_types + chart_spec pieces. Do not install packages or write renderer code unless asked.
  • MCP chart output: if Flint MCP tools are available, default to create_chart_view whenever the user asks to see a chart — it opens an interactive, live-rendered view with a customization panel, and it validates the spec for you. Only fall back to render_chart (PNG/SVG) when the host has no App UI support or the user explicitly wants a static image. Use validate_chart to check a spec without rendering, compile_chart when the user wants backend-native JSON, and list_chart_types when you need the supported chart catalog.
  • Project integration, only when the user asks for code: add Flint to an app, notebook, script, or agentic product, install/import the library, and call an assembler in code. Keep the same ChartAssemblyInput contract, then let the host render the backend result.

Read the full file on GitHub · 571 lines

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. 4d ago First seen · 571 lines · 81 tokens per session scan A 032a2735c683

Subscribe to this mod's changes

flint-chart-author is a skill published in the GitHub repository microsoft/flint-chart (4,094 stars, last pushed 2d ago), licensed MIT. It adds 81 tokens to every session and 7,585 once invoked, about $0.0004 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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