chart-builder

chart-builder is a skill for Claude Code, Codex from NickCrew/Claude-Cortex. It costs 76 tokens per session (3,719 once invoked), scanned A, original, MIT.

Use this skill when creating data visualizations, selecting the right chart type, or generating chart code. Trigger phrases: 'build a chart', 'visualize this data', 'create a graph', 'plot these numbers', 'which chart should I use for'. Not for building interactive dashboards, designing UI components, or creating…

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/nickcrew/claude-cortex/chart-builder
Any agent
npx skills add NickCrew/Claude-Cortex --skill chart-builder
Clone the repo
git clone --depth 1 https://github.com/NickCrew/Claude-Cortex

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 chart-builder

README.md
[![agentmods](https://agentmods.dev/badge/skills/nickcrew/claude-cortex/chart-builder.svg)](https://agentmods.dev/skills/nickcrew/claude-cortex/chart-builder)
Your own site
<a href="https://agentmods.dev/skills/nickcrew/claude-cortex/chart-builder"><img src="https://agentmods.dev/badge/skills/nickcrew/claude-cortex/chart-builder.svg" alt="Measured on agentmods" height="20"></a>
Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,719 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00076 $0.03719
Opus 5 $0.00038 $0.01860
Sonnet 5 $0.00015 $0.00744
Haiku 4.5 $0.00008 $0.00372

Measured today against content hash cdb7d6e52f43, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

chart-builder 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 today.

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.

skills/chart-builder/SKILL.md · 345 lines

How it starts

The opening of the file, as written. The whole thing — 345 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Chart Builder

Overview

This skill provides a systematic approach to data visualization—from choosing the right chart type for your data and message, to implementing it in Python (matplotlib/seaborn) or JavaScript (Chart.js). It covers chart anatomy, color principles, accessibility requirements, and common pitfalls, so every chart communicates its insight clearly and honestly.

When to Use

  • You need to communicate a data insight visually
  • You're unsure which chart type fits your data shape and message
  • You need reproducible chart code in Python or JavaScript
  • You want to improve a chart that isn't communicating clearly
  • You're building a report, slide deck, or embedded visualization

When NOT to Use

  • Building a full interactive BI dashboard (use dashboard-designer skill)
  • Designing data art or infographics for marketing
  • Creating maps or geospatial visualizations (use a GIS tool)
  • Animating data for video production

Quick Reference

Chart Type Best For Avoid When
Bar (vertical) Comparing categories, rankings Too many categories (>12)
Bar (horizontal) Long category labels, rankings Showing trends over time
Line Trends over time, continuous data Categorical/unordered x-axis
Scatter Correlation between two variables Fewer than ~20 data points
Pie / Donut Part-of-whole (max 5 slices) Comparing many segments
Heatmap Matrix of values, correlation tables Audiences unfamiliar with the format
Box plot Distribution comparison across groups Presenting to non-technical audience
Histogram Distribution of a single variable Showing trends or comparisons
Area Cumulative totals over time Multiple overlapping series
Stacked bar Part-of-whole across categories Comparing absolute values

Instructions

Step 1: Choose the Right Chart Type

Answer these questions:

  1. How many variables? 1 (distribution) → histogram/box. 2 (relationship) → scatter/line. 2+ (comparison) → bar/heatmap.
  2. What's the x-axis? Time → line/area. Categories → bar. Continuous numeric → scatter.
  3. What's the message? Trend → line. Ranking → bar. Proportion → pie (≤5 slices). Correlation → scatter.

Read the full file on GitHub · 345 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. today First seen · 345 lines · 76 tokens per session scan A cdb7d6e52f43

Subscribe to this mod's changes

chart-builder is a skill published in the GitHub repository NickCrew/Claude-Cortex (37 stars, last pushed 2mo ago), licensed MIT. It adds 76 tokens to every session and 3,719 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 2026-09-03.