Cnvs Whiteboard Skills MCP Server

cnvs-whiteboard-skills

Agent Skills + MCP server discovery for cnvs.app — the free, no-signup real-time collaborative whiteboard. Any AI agent can read, write, draw, diagram, and subscribe to live human edits on a shared canvas, either through the hosted MCP server or the REST fallback.

Works with Claude Code, Claude Desktop, Cursor, OpenCode / OpenAI Codex, Aider (with MCP plugin), any other MCP-speaking client, and Hermes-family agents.

MCP Server

Endpoint: https://cnvs.app/mcp (Streamable HTTP, protocol 2025-06-18, no auth — the board ID is the access key).

Registered in the official MCP Registry as app.cnvs/whiteboard.

Capabilities

• Tools (10): open_board, get_board, get_preview, add_text, add_link, add_image, draw_stroke, move, erase, wait_for_update. All ten have 1:1 REST mirrors at https://cnvs.app/api/boards/<id>/… for runtimes that can't speak MCP.
• Resources (2): cnvs://board/{id}/state.json (full snapshot, subscribable) and cnvs://board/{id}/preview.svg (visual render, subscribable).
• Subscriptions: resources/subscribe supported with notifications/resources/updated pushed over SSE, debounced ~3 s after activity settles.
• Live machine-readable manifests: /quotas.json, /openapi.json, /llms.txt, /.well-known/mcp.json, /.well-known/mcp/server.json.

Installation

Claude Desktop / Cursor / any MCP client

One-line config — add this to your client's mcpServers object:

{
  "mcpServers": {
    "cnvs": {
      "type": "http",
      "url": "https://cnvs.app/mcp"
    }
  }
}

Claude Code CLI

claude mcp add --transport http cnvs https://cnvs.app/mcp

REST-only (no MCP client)

# Create a board
curl -X POST https://cnvs.app/api/boards

# Add text
curl -X POST https://cnvs.app/api/boards/<id>/texts \
  -H 'Content-Type: application/json' \
  -d '{"x":100,"y":200,"content":"# Hello","author":"ai:myagent"}'

# Long-poll for live changes
curl "https://cnvs.app/api/boards/<id>/wait?timeout_ms=25000"

Full REST reference: /llms.txt, /openapi.json.

Skills included

Two related Agent Skills live in this repo, published under the agentskills.io open standard so they work in any compatible runtime. Install them into ~/.claude/skills/ to teach the agent how to use the MCP server well (preview-before-JSON, REST-over-MCP for writes, author-tag conventions, subscription-then-react loop).

cnvs-whiteboard/ — PRIMARY

Teaches an AI agent how to collaborate on a cnvs.app board in real time:

• Read the shared canvas state
• Draw / diagram / flowchart / annotate — add, update, move, and delete text, links, sticky notes, strokes, images, and Mermaid diagrams (flowcharts, sequence / class / ER diagrams, mind maps, gantt charts, concept maps)
• Render the SVG preview when the board contains drawings
• Subscribe to live human edits via MCP, react via REST

Activates on any cnvs.app board reference (URL https://cnvs.app/#<id>, cnvs://board/<id>/..., or a bare board ID) or phrases like "collaborate on / draw / diagram / annotate / watch a shared whiteboard or canvas."

mcp-listen/ — GENERIC

Push-to-model pump for any Streamable-HTTP MCP server with subscriptions. Opens a session, subscribes to the given resource URIs, and emits one JSON line per notifications/resources/updated event on stdout — designed to be wrapped by Claude Code's Monitor tool so every server push becomes an in-chat notification (no polling, no log tailing).

Not cnvs-specific. Works against file watchers, remote queues, task runners, anything exposing resources/subscribe over MCP. cnvs-whiteboard delegates its push channel here.

Install the skills

# cnvs-whiteboard (SKILL.md only — no deps)
mkdir -p ~/.claude/skills/cnvs-whiteboard && cd ~/.claude/skills/cnvs-whiteboard
curl -O https://cnvs.app/cnvs-whiteboard/SKILL.md

# mcp-listen (SKILL.md + scripts/ + npm install)
mkdir -p ~/.claude/skills/mcp-listen && cd ~/.claude/skills/mcp-listen
curl -O https://cnvs.app/mcp-listen/SKILL.md \
     -O https://cnvs.app/mcp-listen/package.json \
     --create-dirs -o scripts/listen.mjs https://cnvs.app/mcp-listen/scripts/listen.mjs
npm install

Alternatively git clone this repo and cp -r .claude/skills/* ~/.claude/skills/ — the .claude/skills/ directory contains symlinks into cnvs-whiteboard/ and mcp-listen/ for Claude Code's expected layout.

Spec compliance

Both skills follow the agentskills.io spec:

• name matches the containing directory name
• description under 1024 characters, imperative phrasing, explicit trigger keywords
• scripts/ subdirectory for bundled code (mcp-listen)
• license: MIT, compatibility field declared, cross-references in each skill's "Related skills" section to prevent activation overlap

Why two skills

Earlier versions had a single page (/skill-cnvs.md on cnvs.app — now a legacy redirect). Splitting into two coherent units follows the spec's "design coherent units" best practice:

• cnvs-whiteboard owns the cnvs.app-specific workflow (read / write / render / gotchas).
• mcp-listen owns the generic push-to-model pattern (usable against any MCP server).

Cross-references keep them pairing cleanly: cnvs-whiteboard mentions mcp-listen as its delegated push channel; mcp-listen mentions cnvs-whiteboard as the companion for cnvs-specific work. No activation overlap in practice.

Canonical sources

Skills are also served live at:

• https://cnvs.app/cnvs-whiteboard/SKILL.md
• https://cnvs.app/mcp-listen/SKILL.md
• https://cnvs.app/mcp-listen/scripts/listen.mjs
• https://cnvs.app/mcp-listen/package.json

The cnvs.app URLs are the canonical install targets for curl-based installers; this GitHub repo is the reference for aggregators that crawl public sources (skills.sh, etc.) and for users who prefer git clone.

Discovery surfaces

• Official MCP Registry: app.cnvs/whiteboard — browse
• cnvs.app /.well-known/mcp.json — links both skills
• cnvs.app /.well-known/mcp/server.json — MCP Registry entry with publisher-provided _meta.skills[]
• cnvs.app /llms.txt — LLM-friendly full reference
• Community skill registries — daymade/claude-code-skills, majiayu000/claude-skill-registry (submitted)
• Lobehub (used by Hermes agent) — both skills imported; MCP server submitted

License

MIT. See LICENSE.