MatPlotLibNet.Mcp 1.25.0

MatPlotLibNet.Mcp

mcp-name: io.github.xkqg/matplotlibnet

An MCP (Model Context Protocol) server for MatPlotLibNet. It gives an AI agent (Claude Code, VS Code, Claude Desktop, or any other MCP host) five tools:

The server communicates over stdio. It is a .NET tool: a host runs it with dnx MatPlotLibNet.Mcp (the .NET 10 SDK resolves and starts it), or with dotnet tool exec MatPlotLibNet.Mcp.

{
  "servers": {
    "MatPlotLibNet.Mcp": {
      "type": "stdio",
      "command": "dnx",
      "args": ["MatPlotLibNet.Mcp", "--yes"]
    }
  }
}

The spec

The spec is the library's own figure JSON: the same document that figure.ToJson() writes and ChartSerializer.FromJson reads. The agent can therefore ask for any chart the library can draw:

{
  "width": 800, "height": 600, "title": "Revenue",
  "subPlots": [{
    "series": [{ "type": "line", "xData": [1, 2, 3, 4, 5], "yData": [2, 4, 3, 5, 1], "label": "Q1" }]
  }]
}

The server validates the spec before it renders. It rejects an unknown field, an unknown chart type, a misspelled enum value, a colour the library does not know, or a missing size. The error message names the field that is wrong, so the model can correct the spec instead of receiving a blank picture. It checks every axis and every series of a subplot the same way, a left-hand Y axis or the fifth right-hand one included, and the message names the place (for example $.subPlots[0].leftYAxes[1].series[0].type). A chart can have any number of Y axes on either side.

A spec's dpi sizes the PNG it renders, as WithDpi does in code: an 800 by 600 spec at 192 dpi is a 1600 by 1200 pixel picture with the same layout, drawn finer. SVG and PDF ignore it. The canvas ceiling (4,000 by 4,000 pixels) holds for the picture the spec draws, so its width and height times dpi / 96 must stay inside it: 400 wide at 960 dpi is exactly 4,000 pixels. A spec over the ceiling is refused with a message that names dpi, the size it would draw and the ceiling.

What comes back

render_chart returns the PNG as an image block. Beside it, it returns a short text summary (chart types, series, axis ranges), so a model that cannot see the image still knows what it made. SVG and PDF output is large, so it goes to a file through save_chart and is never returned inline.

The SVG this server writes stores text as glyph outlines (<path>), not as <text> elements. This is because the PNG backend is loaded in the same process, and the library then embeds its own font so that the drawing is identical everywhere.

Limits

• save_chart writes only under one directory: the system temp directory, or the one named by the MATPLOTLIBNET_MCP_OUTPUT_ROOT environment variable. It never overwrites an existing file unless asked.
• Arabic and Hebrew text work without setup. For Devanagari, Thai, Chinese, Japanese or Korean, name font files or directories of font files in the MATPLOTLIBNET_FONTS environment variable, separated by ;; they are registered when the server starts. A bad entry is logged and skipped.
• The server refuses a canvas larger than the documented ceiling, and the error message states the ceiling.

License

MIT — see the repository.