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.
npx skills add NickCrew/Claude-Cortex --skill chart-buildergit clone --depth 1 https://github.com/NickCrew/Claude-CortexWrote 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.
[](https://agentmods.dev/skills/nickcrew/claude-cortex/chart-builder)<a href="https://agentmods.dev/skills/nickcrew/claude-cortex/chart-builder"><img src="https://agentmods.dev/badge/skills/nickcrew/claude-cortex/chart-builder/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.
<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="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00076 | $0.03719 |
| Opus 5.5 | $0.00030 | $0.01488 |
| Sonnet 5.5 | $0.00015 | $0.00744 |
| Haiku 4.5 | $0.00008 | $0.00372 |
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 1mo 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.
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:
- How many variables? 1 (distribution) → histogram/box. 2 (relationship) → scatter/line. 2+ (comparison) → bar/heatmap.
- What's the x-axis? Time → line/area. Categories → bar. Continuous numeric → scatter.
- What's the message? Trend → line. Ranking → bar. Proportion → pie (≤5 slices). Correlation → scatter.
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.
- 1mo ago First seen · 345 lines · 76 tokens per session scan A cdb7d6e52f43
chart-builder is a skill published in the GitHub repository NickCrew/Claude-Cortex (56 stars, last pushed 3mo ago), licensed MIT. It adds 76 tokens to every session and 3,719 once invoked, about $0.0003 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 2026-09-03.
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