Chart creation foundations

These tools render BI/financial-analyst-grade charts and diagrams that show up live in the chat AND save as high-DPI PNGs in the user's queen session dir.

The embedding contract — one rule

To put a chart in chat, call chart_render. The chat reads result.spec and renders the chart live in the message bubble. The download link is result.file_url. Do not write ![chart](...) image markdown by hand — the tool's result drives the UI.

That's it. One tool call, one chart in chat, one file on disk. No two-step "remember to also save it" pattern. The chat's chart-rendering UI is fed by the tool result envelope automatically.

When to chart at all

Chart when the data is visual at heart: trends over time, distributions, comparisons across categories, hierarchies, flows, geo. Skip the chart when:

• The point is one number → just say it. ("Revenue was $4.2M, up 12% YoY.")
• The point is a ranking of 5 things → use a markdown table with bold and emoji indicators.
• The data is so noisy a chart would mislead → describe the takeaway in prose.

A chart costs the user attention. It must repay that cost with a takeaway they couldn't get from prose.