Canvs MCP Server

Creates elements on a canvas. Creates a new canvas if room_id is omitted, or adds to the existing canvas if room_id is provided. Use cases: wireframes, UI mockups, freeform illustrations, standalone shapes, and manual layouts that Mermaid does not cover well. For diagrams Mermaid can express, use add_elements_from_mermaid instead. Element types: rectangle, ellipse, diamond, arrow, line, freedraw, text, image. Rich text: the text field supports limited HTML for text elements and rectangle/ellipse/diamond shape labels. Supports the rich-text plugin HTML subset: <b>/<strong>, <i>/<em>, <u>, <br>, <div>/<p>, <ul>/<ol>/<li>, <a href>, <font color>, and <span style="color, background/background-color, font-size, font-family">. Use textAlign for left/center/right alignment; avoid unsupported HTML/CSS. TEXT IN SHAPES: use containerId on text element pointing to shape id. ARROWS: Position at EDGE of source shape. Auto-bound within 30px. Colors: strokeColor, backgroundColor (hex).

Creates diagram elements from a Mermaid definition. Creates a new canvas if room_id is omitted, or adds to the existing canvas if room_id is provided. Preferred over add_elements for new diagrams and large changes to existing diagrams whenever the content can be represented in Mermaid. Supports: flowchart, graph, flowchart-elk, sequenceDiagram, classDiagram, classDiagram-v2, stateDiagram, stateDiagram-v2, erDiagram, journey, gantt, pie, gitGraph, mindmap, timeline, C4Context, C4Container, C4Component, C4Dynamic, C4Deployment, sankey, sankey-beta, quadrantChart, xychart, xychart-beta, requirement, requirementDiagram, kanban, architecture, block, block-beta, packet, packet-beta, radar-beta, treemap, info. Example: "flowchart TD\n A[Start] --> B{Decision}\n B -->|Yes| C[OK]\n B -->|No| D[Cancel]"

Delete elements from a canvas. Requires room_id from a previous Canvs tool result. Pass ids array of element IDs to delete.

Query elements on a canvas. Requires room_id from a previous Canvs tool result. Returns elements matching optional filters. Use this before update_elements when making small edits to existing diagrams. If no browser has the canvas open, returns an error — ask the user to open the canvas URL in their browser and retry.

Update elements on a canvas. Requires room_id from a previous Canvs tool result. Pass elements array with id and fields to update. IMPORTANT: in each update object ONLY `id` is required; all other fields are optional patch fields. Include ONLY elements that need changes; elements omitted from the request remain unchanged on the board. Prefer this tool for SMALL edits to existing diagrams (rename/move/restyle a few elements), typically after query_elements.

Returns guidance on diagram-creation workflow and tool selection: how to choose between Mermaid and manual element creation, and the recommended iteration workflow. Consult before building complex diagrams.