mcp server

cnvs.app

Real-time collaborative whiteboard — AI agents and humans edit the same board live over MCP.

Description as published by the maintainer. Source

• version 1.0.2
• active

active — Most recent push to the repository was 2026-07-15.

What this server can do

25 functions, named and described by the server itself. Parameter names are shown because they say more about what a function does than its name usually does.

add_image(x, y, id, width, author, height, board_id, data_url, access_key, thumb_data_url)

Place a raster or SVG image on the board at (x, y) with explicit width/height in board pixels. `data_url` MUST be a `data:image/(png|jpeg|gif|webp|svg+xml);base64,...` string ≤ ~900 kB; hosted URLs are not accepted. Strongly recommended: also pass a tiny `thumb_data_url` (≤8 kB JPEG/PNG/WebP, ~64 px on the long edge) — it is embedded into the SVG preview so OTHER AI viewers (and you, on later `get_preview` calls) can actually see the image instead of a placeholder box. Required: board_id, x, y, width, height, data_url.

add_link(x, y, url, author, board_id, access_key)

Drop a URL capsule onto the board — rendered as a clickable pill showing the hostname. Use this instead of `add_text` when the node is just a link; the capsule styling signals clickability to humans. Same coordinate rules as `add_text` (+x right, +y down). Required: board_id, x, y, url.

add_text(x, y, id, color, width, author, postit, content, diagram, board_id, access_key)

Create a NEW text node, or update an existing one (pass the same `id` to overwrite content/position in place — preferred over creating a duplicate). Supports cnvs markup (Markdown-ish) and Mermaid diagrams in the content. When using Mermaid, the ENTIRE content of this text node must be a single Mermaid diagram (one ```mermaid fenced block and nothing else — no heading, no prose before or after). If you need prose + a diagram, create two separate text nodes. `postit: true` renders as a yellow sticky; `diagram: true` renders as a framed box (2px border in the text colour, centred text) — the two are mutually exclusive. Coordinates are in board-world pixels, +x right, +y DOWN; pick a spot that does not overlap existing items (check `get_preview` first). Default width auto-fits content up to ~320 px; pass `width` for explicit wrapping (160–4096). Keep content under 100 000 chars. Required: board_id, x, y, content.

create_board(lock, mode, author, content, template, autolayout)

Create a fresh board in ONE call — optionally pre-filled with content, auto-laid-out, and/or PIN-locked at create time. Mirrors the extended `POST /api/boards` REST body exactly (same server-side implementation). With no arguments it returns a blank draw board; `mode: 'todo'` (+ optional `template`) seeds a kanban board. `content` imports initial items atomically: everything is validated FIRST and the board is created only if every item passes — on any invalid item you get a structured error naming its kind + index and NOTHING is created. `autolayout: true` (draw mode) fills in x/y for texts/images that omit them (deterministic masonry grid; explicit coordinates are never touched). `lock: 'write'|'all'` locks the board atomically with creation and returns the plaintext `access_key` ONCE — there is no recovery. The response's `imported` counts confirm what was created, `ids` returns the server-minted item ids per kind in the order you supplied them (index i of `ids.texts` is the id created for `content.texts[i]`; `ids.columns` is empty when the columns came from the template seed, and lanes have no id — they are keyed by board + lane index), and `embed_url` (the `?embed=1#<id>` iframe view) is returned for any board readable without a key — it is omitted for `lock:'all'` boards, whose embed frame can't read the board anonymously. Prefer this over open_board + N per-item calls when you are building a whole board from scratch.

create_column(lane, sort, color, title, author, board_id, access_key)

Add a kanban column (swimlane) to a 'todo' board. Generates and returns a stable column id. `sort` is a float ordering key (ascending); omit to default to 0. `lane` is an integer row index for multi-row layouts (defaults to 0). `color` is an optional title color ('red' / 'blue' / 'green', or 'auto' / omit for default). To rename, reorder, recolor or move between lanes later use `update_column`. Required: board_id, title.

create_task(done, name, sort, author, assignee, board_id, due_date, priority, column_id, access_key, description)

Create a task (card) in a column on a 'todo' board. Generates and returns a stable task id. `column_id` must reference an existing column (see `list_tasks`). `description` is free-form prose stored on the card; `priority` is one of 'H' | 'M' | 'L' (omit for none); `due_date` is an ISO 8601 date string; `assignee` is free text (name / initials / email). `sort` is a float ordering key within the column (ascending), defaulting to 0. Required: board_id, column_id, name.

create_tasks(tasks, author, board_id, access_key)

Bulk-create multiple task cards in one call — far cheaper than calling `create_task` N times. Pass `tasks`: an array of task objects, each with `column_id` (required) + the same fields `create_task` accepts (`name`, `description`, `due_date`, `priority`, `assignee`, `done`, `sort`). Returns the array of created ids in order. Stops at the first invalid item and reports its index; items before it are still created (not transactional). Required: board_id, tasks.

delete_column(id, board_id, access_key)

Delete a kanban column by id. Tasks in the column are removed with it. Get the id from `list_tasks`. Required: board_id, id.

delete_task(id, board_id, access_key)

Delete a task (card) by id. Get the id from `list_tasks`. Required: board_id, id.

draw_stroke(id, color, author, points, board_id, access_key)

Draw a freehand stroke on the board. Use for arrows, underlines, connector lines, annotations, or simple shapes — a straight line needs two points, a rough circle wants ~20. Stroke width is fixed at 3 px; `color` is a NAME, not hex (case-insensitive): 'auto'/''/'black'/omitted for theme-aware ink, or 'red', 'blue', 'green', 'orange', 'yellow', 'pink', 'purple', 'maroon', 'brown', 'gray', 'lightgray', 'teal', 'sage', 'sky', 'lavender' — anything else (including a literal hex like '#ff0000') silently clamps to auto. Accepts three equivalent point formats — pick whichever your MCP client serialises cleanly: nested `[[x,y],[x,y],...]`, flat `[x1,y1,x2,y2,...]`, or a JSON string of either. Some clients (Claude Code as of 2026-04) drop nested arrays during tool-call serialisation, so prefer the flat form or the JSON-string form when in doubt. To delete a stroke later, use `erase` with `kind: 'line'` and the id returned here. Required: board_id, points.

erase(id, kind, board_id, access_key)

Delete a single item by id. `kind` MUST match the item type: 'text' for text nodes, 'line' for freehand strokes, 'image' for images — the wrong kind silently targets the wrong table and is a common mistake. Get the id + type from `get_board` (texts[], lines[], images[]). There is no bulk/erase-all tool: loop if you need to delete multiple items. Required: board_id, id, kind.

export_tasks(format, board_id, access_key)

Export a 'todo' board's columns + tasks as a single text document. `format` is 'markdown' (a checklist grouped by column, the default) or 'csv' (one row per task with column/name/priority/assignee/due_date/done). Returns the rendered text. Same data as the GET /api/boards/<id>/tasks.md and tasks.csv REST endpoints. Required: board_id.

get_board(board_id, access_key)

Full structured JSON state of a board: texts (id, x, y, content, color, width, postit, author), strokes (id, points, color, author), images (id, x, y, width, height, dataUrl, thumbDataUrl, author; heavy base64 >8 kB elided to dataUrl:null, tiny images inlined). Use this for EXACT ids/coordinates/content (needed for `move`, `erase`, editing a text by id). For visual layout (where is empty space? what overlaps?) call `get_preview` instead — it's much cheaper for spatial reasoning than a huge JSON dump. Required: board_id.

get_preview(board_id, access_key)

Compact schematic SVG render of the board (typically a few kB even for dense boards). Returns both an image/svg+xml content block (you can SEE it) and the raw SVG text. CALL THIS any time you need to understand where things are — before placing new items, before deciding whether the canvas is crowded, before picking a free region. AI-authored items get a purple border so you can tell which contributions were yours. For precise text content prefer `get_board`. Required: board_id.

list_tasks(board_id, access_key)

Read the full kanban state of a 'todo' board: `{ mode, columns, tasks }`, both ordered by their `sort` key (ascending). Each task carries its hot fields (name, due_date, priority, assignee, done, column_id, sort) plus an opaque `content` JSON string (holds the description). Use this to get exact column/task ids before updating, moving or deleting. Required: board_id.

move(x, y, id, kind, board_id, access_key)

Reposition an existing item to a new (x, y) without retyping its content. Works for every item kind: `text` and `link` set the top-left to (x, y); `line` translates every point so the stroke's bounding box top-left lands at (x, y); `image` sets the top-left like text. `kind` defaults to `text` for backward compat with older callers. Find the id + kind via `get_board`. Prefer `move` over re-creating an item when only the location changes — it preserves the id, content, author and avoids a round-trip of base64 bytes for images. Required: board_id, id, x, y.

move_task(id, sort, board_id, column_id, access_key)

Move a task to a column at a given sort position — the kanban drag-and-drop primitive. `column_id` is the destination column and `sort` its float order key (ascending) within that column. Required: board_id, id, column_id, sort.

open_board(url_or_id, access_key)

ALWAYS call this first when given a board URL or ID. Resolves the canonical board id and auto-creates the board row if it does not exist yet. Returns a summary (item counts, authors). After this, call BOTH `get_preview` and `get_board` before editing so you can see the layout visually AND know the exact ids/coordinates — do not skip `get_preview`, otherwise you will place new items blindly on top of existing ones. Required: url_or_id.

query_tasks(done, overdue, assignee, board_id, priority, due_after, access_key, due_before)

Read tasks from a 'todo' board with server-side filtering — handy for 'what's overdue?' / 'what's assigned to X?' without pulling the whole board. All filters are optional and AND together: `assignee` (exact match), `priority` ('H'|'M'|'L'), `done` (boolean), `overdue` (true → due_date strictly before today, not done), `due_before` / `due_after` (ISO date window on due_date). Returns `{ boardId, mode, tasks }` — tasks ordered by sort, each with the same fields as `list_tasks`. Required: board_id.

set_board_mode(mode, board_id, template, access_key)

Choose whether this board is a freeform whiteboard ('draw', the default) or a kanban task board ('todo'). Mode is switchable WHENEVER the board is empty of real content: drawings (text/strokes/images) and tasks. Empty or seeded columns DON'T count (switching to 'draw' clears them), so a cleared board can be switched again, and you can flip draw<->todo freely until the first stroke/text/image or task lands. Setting 'todo' auto-seeds three starter columns (To do / In progress / Done). Returns `{ mode, columns }`. Use the task/column tools (`create_task`, `create_column`, …) once the board is in 'todo' mode. Required: board_id, mode.

set_column_width(width, board_id, access_key)

Set the shared kanban column width in pixels for a 'todo' board (all columns share one width). Clamped to [200, 480]. Read the current value as `colWidth` from `list_tasks`. Required: board_id, width.

set_lane(lane, title, author, board_id, access_key)

Set (or clear) the title of a kanban row (lane). Lanes group columns into horizontal swimlanes; a lane is identified by its integer `lane` index (the same index columns carry). Pass a `title` to name the row, or an empty string to clear it. Read current lane titles + the shared column width via `list_tasks`. Required: board_id, lane.

update_column(id, lane, sort, color, title, author, board_id, access_key)

Rename, reorder, recolor or move an existing kanban column. Requires the column `id` (from `list_tasks`). Pass `title`, `sort`, `lane` and/or `color` to change them. Required: board_id, id.

update_task(id, done, name, sort, author, assignee, board_id, due_date, priority, column_id, access_key, description)

Update an existing task by `id` (from `list_tasks`). Pass only the fields you want to change: `name`, `description`, `due_date`, `priority` ('H'|'M'|'L'), `assignee`, `done` (true once completed), `column_id` (to reassign), `sort`. To move a card between columns while setting its order, `move_task` is the dedicated tool. Required: board_id, id.

wait_for_update(board_id, access_key, timeout_ms)

Long-poll: blocks until the next edit lands on this board, then returns. WHEN TO CALL THIS: if your MCP client does NOT surface `notifications/resources/updated` events from `resources/subscribe` back to the model (most chat clients do not — they receive the SSE event but don't inject it into your context), this tool is how you 'wait for the human' inside a single turn. Typical flow: you draw / write what you were asked to, then instead of ending your turn you call `wait_for_update(board_id)`. When the human adds, moves, or erases something, the call returns and you refresh with `get_preview` / `get_board` and continue the collaboration. Great for turn-based interactions (games like tic-tac-toe, brainstorming where you respond to each sticky the user drops, sketch-and-feedback loops, etc.). If your client DOES deliver resource notifications natively, prefer `resources/subscribe` — it's cheaper and has no timeout ceiling. BEHAVIOUR: resolves ~3 s after the edit burst settles (same debounce as the push notifications — this is intentional so drags and long strokes collapse into one wake-up). Returns `{ updated: true, timedOut: false }` on a real edit, or `{ updated: false, timedOut: true }` if nothing happened within `timeout_ms`. On timeout, just call it again to keep waiting; chaining calls is cheap. `timeout_ms` is clamped to [1000, 55000]; default 25000 (leaves headroom under typical 60 s proxy timeouts). Required: board_id.

Last successful function declaration observed on 2026-08-13. Source: https://cnvs.app/mcp. We list what the server declared; we do not call any of these functions.

Endpoint status observed on 2026-08-13. Source: https://cnvs.app/mcp.

Signals

These are separate measurements of different things. They are deliberately not combined into one score, because a popularity number that mixes website traffic with saves and stars cannot be checked or acted on.

Where to get it

• Repository — https://github.com/lksrz/cnvs-whiteboard-skills
• Website — https://cnvs.app
• Remote endpoint (streamable-http) — https://cnvs.app/mcp

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