noddle draw

noddle draw MCP server

Lets an AI agent (Claude Code, Claude Desktop, or any MCP client) work on a board alongside you: read, create and edit boards, browse version history, and comment like any other collaborator.

noddle draw is anonymous. There are no accounts and no tokens. A board id (12 hex chars) or a board URL is the capability. The agent can open any board you give it, and anyone holding the link of a board the agent creates can open it too. The agent signs its comments and version snapshots with NODDLE_AGENT_NAME.

• Stdlib-only Python ≥ 3.9 (urllib + json), so there is nothing to install.
• stdio transport: one JSON-RPC 2.0 message per line. stdout carries only protocol messages, and logs go to stderr.
• MCP protocol, dual-era:
  • 2026-07-28 (modern, stateless): every request carries _meta["io.modelcontextprotocol/protocolVersion"] + clientCapabilities. The server implements server/discover, and sets resultType and _meta["io.modelcontextprotocol/serverInfo"] on every result, plus ttlMs/cacheScope on list/read results. An unsupported version returns -32022 UnsupportedProtocolVersion.
  • Legacy initialize handshake: 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05. The server answers with the client's version when it supports it, and otherwise with 2025-11-25. ping works in this mode. JSON-RPC batches are accepted only for 2025-03-26, the only revision that allowed them.

1. Register

Claude Code (from the repo root; an absolute script path is more robust):

claude mcp add noddle -- python3 mcp/noddle_mcp.py# a self-hosted instance instead of draw.noddle.dev:claude mcp add noddle --env NODDLE_BASE_URL=http://127.0.0.1:8000 -- python3 mcp/noddle_mcp.py

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json) or a project .mcp.json use the same shape:

{  "mcpServers": {    "noddle": {      "command": "python3",      "args": ["/absolute/path/to/noddle-draw/mcp/noddle_mcp.py"],      "env": { "NODDLE_BASE_URL": "https://draw.noddle.dev" }    }  }}

MCP Bundle (one-click install in Claude Desktop and other MCPB clients): download noddle-draw.mcpb from the latest mcpb-v* release and open it. It needs only Python 3.10+ (standard library, no install step).

From a checkout (pyproject.toml here):

uvx --from ./mcp noddle-draw-mcp       # or: pipx install ./mcp && noddle-draw-mcp

The server is listed in the official MCP Registry as dev.noddle/draw (see Releasing).

CLI: --help, --version, --list-tools (prints the tool definitions as JSON). Exit codes: 0 when stdin closes (normal shutdown), 2 for bad configuration.

2. Tools

Every tool returns structuredContent that conforms to its outputSchema, plus the same JSON as a text block. Board tools also return a resource_link to noddle://board/{id} (revisions ≥ 2025-06-18). Wherever a tool takes doc_id, you can pass either the 12-hex id or the board URL ({base}/d/{id} or /embed/{id}). A URL on a different origin than NODDLE_BASE_URL is refused.

There is deliberately no list_boards and no delete: the API has neither. Link access is not discovery, and an anonymous board has no owner who could be trusted to delete it. Writes to a board whose link is view-only fail with a 403 tool error.

Diagram payloads are pass-through. The server checks only the envelope ({pages:[{id,nodes,edges}]} or legacy {nodes,edges}, with string ids). Node and edge fields are forwarded untouched, so new editor fields (e.g. the freedraw kind with points, or curved routing) work without a server update. See DiagramNode / DiagramEdge in contracts/openapi.yaml.

Errors:

• Bad arguments, API failures (400/403/404/413/422/429/503) and conflicts come back as isError: true tool results that the model can act on.
• Protocol errors use standard JSON-RPC codes: unknown tool or invalid params -32602, unknown method -32601, malformed JSON -32700, invalid request -32600.

3. Resources & prompts

• Resources: resources/list lists the boards this session has created, read or edited, as noddle://board/{id} (application/json, lastModified). It starts empty, because the API has no listing. resources/templates/list exposes noddle://board/{doc_id}, so a client can read any board by id. resources/read returns the same JSON as get_board. An unknown board returns -32602.
• Prompts:
  • design_board(topic, notes?): generate → sanity-check → create_board → reply with the url.
  • review_board(doc_id): embeds the board as a resource and asks for a critique posted as anchored comments.

4. Example (Claude Code)

> Create a board "Payment flow" with Client → API Gateway → Payment Service → Database,  then comment on the Database node reminding the team to review indexes.
Claude: generate_diagram(text="Client -> API Gateway -> Payment Service -> Database")        → create_board(name="Payment flow", diagram=…)        → add_comment(doc_id, body="Please review indexes for the payments table", node_id="db")        → returns https://draw.noddle.dev/d/{id}

Comments reach an open board in realtime. A diagram written with update_board shows up when the board is reloaded.

5. Tests

python3 -m pytest mcp -q        # or: python3 -m unittest discover mcp

test_noddle_mcp.py runs the real server over stdio against a fake in-process REST backend. It covers version negotiation (modern and legacy), schema validity, read and write tools, board-URL ids, view-only links, resources, prompts, BYOK header forwarding and error paths. It also asserts that stdout carries only JSON-RPC, that no request ever carries an Authorization header, and that a BYOK key never leaks into output or logs.

Releasing

mcp/server.json is the registry listing (dev.noddle/draw); it points at the MCP Bundle attached to a GitHub release. The dev.noddle/* namespace is verified over HTTP: noddle.dev serves the publisher's ed25519 public key at /.well-known/mcp-registry-auth.

1. Bump the version everywhere, all equal: __version__ in noddle_mcp.py, version in mcpb/manifest.json, version in pyproject.toml, and version in server.json. Registry versions are immutable; a metadata-only fix uses a suffix such as 1.0.0-1.
2. Build the bundle: mcp/build_mcpb.sh → mcp/dist/noddle-draw.mcpb (prints its SHA-256).
3. Create the release with that exact file: gh release create mcpb-v<version> mcp/dist/noddle-draw.mcpb --title "MCP server <version>".
4. In server.json, set the package identifier to the release download URL and fileSha256 to the printed hash, then publish with the namespace key holder's mcp-publisher login http --domain noddle.dev --private-key … and mcp-publisher publish mcp/server.json.

Notes

• update_board keeps the stored SVG preview. The preview refreshes on the next save in the editor.
• Cross-origin HTTP redirects are refused, so a BYOK key is never forwarded to another host. A BYOK key over plain http to a non-loopback host logs a warning.
• generate_diagram sends text to an AI provider. Never pass customer PII, credentials or account numbers.