Chart to Data connector for Claude
The connector lets Claude, or any assistant that speaks the Model Context Protocol (MCP), read the data out of the charts in a PDF for you. Give it the address of a paper and ask for the numbers: they come back exactly, read from the drawing inside the PDF.
Connect it
- In Claude, open Settings, then Connectors.
- Choose to add a custom connector and paste this address: https://charttodata.com/mcp
- There is no sign-in and no key. Start a conversation and ask for the data in a chart.
What to ask
- Read the charts in https://charttodata.com/samples/efficiency-versus-load.pdf and give me the values as a table.
- Get the survival curves and the numbers at risk from https://charttodata.com/samples/survival-curve.pdf.
- Read only pages 4 and 7 of the PDF at an address you give, and compare the two charts.
The tool
- read_charts_in_pdf reads every chart drawn in a PDF from the drawing itself. The values are exact and no AI model is involved. It takes the PDF's web address and, if you want, the pages to read.
- It only reads. It changes, stores and sends nothing on your behalf.
What comes back
For each chart: its kind and title, both axes with their labels and ranges, each series by name, and every point with its error bars. A survival curve comes with its number-at-risk table. Each chart says how it was read: exact when tick marks or gridlines pin its axes, close when the axes had to be placed from their labels alone.
Limits
- A PDF is named by its public web address (https). The connector cannot read a file on your computer or one behind a sign-in.
- Up to 20 MB a file, and up to 40 pages at a time.
- It reads charts the PDF holds as drawings, which is most figures in recent papers. A chart that is only a picture inside the PDF, or a scan, is not found: read those on the site.
- The kinds of chart read are bar charts, line charts, scatter plots, pie charts and survival curves, with log axes, date axes, two y axes and error bars.
Privacy
The connector receives only what the assistant sends it: the address of a PDF and the pages to read. It does not see your conversation. It fetches the file, reads it with our own program, and deletes it as soon as the reading ends. The file goes to nobody else.
To limit use, a scrambled form of the calling internet address is kept for a few days. It cannot be turned back into the address.
Questions
Does it need an account or an API key?
No. Add the address as a connector and it works.
What does it cost?
Nothing. Reading the charts in a PDF is free.
How exact is it?
When a PDF holds the chart as a drawing (most figures in papers do), the values are read from the drawing itself. Nothing is estimated from pixels, so a point is as precise as the file is.
Can it read a screenshot or a picture of a chart?
Not through the connector. On the site a picture of a chart is read by an AI model and drawn back on the picture for you to check; one a day is free.
Who do I ask for help?
Write to support@charttodata.com.