maidr MCP server

maidr-mcp

<!-- mcp-name: io.github.xability/maidr-mcp -->

An MCP server that shows accessible maidr charts inside ChatGPT and Claude conversations, and lets the conversation's model move the reader through them and run the chart's commands for them.

The model calls show_chart with the data, and the chart appears in the conversation as an MCP App. A blind or low-vision reader Tabs into it and explores it the way they explore any maidr chart: arrow keys, screen reader, sonification, braille. Three things then happen through the model:

• The model can take the reader somewhere. When the reader asks for "the highest bar", the model calls maidrgetlayerdata to find it and maidrnavigate to move there, and maidr announces the point by speech, braille and sound. When the reader is typing to the model rather than in the chart, it passes focus: true, since they asked to be taken there, and maidr moves their keyboard focus into the chart to make the move.
• The model can press the chart's keys for the reader. When the reader asks to turn braille off, play the chart, or jump to the lowest value, the model calls maidrlistcommands to find the command and the reader's current modes, and maidrruncommand to run it. maidr announces the result as if the reader had pressed the key, and the model tells them which key that was.
• The model knows where the reader is. As the reader moves, the chart tells the model their position, so "what is this point?" needs no tool call. Within a turn, maidrlistcharts reads it live.

Experimental. Checked end to end in the MCP Apps SDK's reference host (below). Not yet checked in claude.ai or ChatGPT.

How it works

1. showchart draws the chart on the server with matplotlib and py-maidr, so the model sends numbers rather than an SVG. The SVG reaches the chart view in the tool result's meta, which is not added to the model's context.
2. The view loads maidr.js and the MCP Apps SDK from cdn.jsdelivr.net, the only domain its CSP declares, at pinned versions.
3. maidr.js registers its own WebMCP tools on document.modelContext. No host hands a view's tools to the model yet (ext-apps#797), so the view supplies document.modelContext itself. Each server tool of the same name relays its call to the view that is open:

• the model calls the server tool;
• the view polls an app-only tool, picks up the call, runs maidr's tool, and posts maidr's answer back;
• that answer becomes the model's tool result.

The poll is a long poll: the server holds it for up to 20 seconds until a call comes, so the call reaches the chart at once. If the host cuts or refuses a request held that long, the view falls back to short polls, which the server answers at once, one every 2 seconds, so the model's call is still answered within the 10 seconds the server waits for the chart. The view tries a long poll again after a minute, and waits twice as long after each one the host cuts.

Shortened. The full README is on GitHub.