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excalidraw-room-mcp

by bjcoombs
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Remote

join_room

Join an existing Excalidraw live-collaboration room via its link and load the current scene; returns your assigned handle.

Instructions

Join an existing excalidraw.com live-collaboration room from its link (the URL with #room=,). Loads the current scene from a connected peer, or from the room's persisted copy if nobody else is present. The result states the handle this server took in the room.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
linkYesCollaboration link, e.g. https://excalidraw.com/#room=abc...,key...
handleNoName to appear as in the room: lowercase letters, digits and hyphens, 1 to 32 characters. Made unique against the agents already in the room by appending -2, -3, and the result text states the handle taken. Defaults to root-claude.
originNoOrigin header to present to the relay. Defaults to https://excalidraw.com, which the public relay requires.
serverUrlNoRelay URL. Defaults to excalidraw.com's public relay.
nearbyRadiusNoHow far a neighbourhood query reaches around a mention, in canvas px, and the distance placement keeps between clusters. 250 by default; room_status reports it, and list_mentions, wait_for_mention, show_room, read_scene near and snapshot_scene near use it when they are given no radius of their own.
agentReplyDepthNoHow many agent replies deep a chain an agent started may run before this agent stops hearing it, 0 to 5. 1 by default, so an agent may answer another agent once and the conversation goes on only if a person writes again; 0 means agent-started chains are never answered, even with answerAgentMentions on. A chain a person started is never bounded. This agent takes the bound at its own join and applies it to what it hears; it is not synchronised across the room, so two agents in one room may hold different bounds. room_status reports it as "agentReplyDepth: <n>".

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.8.0
    • addedInput schema / properties / agentReplyDepth
      Added value: +{
+  "description": "How many agent replies deep a chain an agent started may run before this agent stops hearing it, 0 to 5. 1 by default, so an agent may answer another agent once and the conversation goes on only if a person writes again; 0 means agent-started chains are never answered, even with answerAgentMentions on. A chain a person started is never bounded. This agent takes the bound at its own join and applies it to what it hears; it is not synchronised across the room, so two agents in one room may hold different bounds. room_status reports it as \"agentReplyDepth: <n>\".",
+  "maximum": 5,
+  "minimum": 0,
+  "type": "integer"
+}
  2. Changed2 schema fields changedv0.7.1
    • addedInput schema / properties / handle
      Added value: +{
+  "description": "Name to appear as in the room: lowercase letters, digits and hyphens, 1 to 32 characters. Made unique against the agents already in the room by appending -2, -3, and the result text states the handle taken. Defaults to root-claude.",
+  "type": "string"
+}
    • addedInput schema / properties / nearbyRadius
      Added value: +{
+  "description": "How far a neighbourhood query reaches around a mention, in canvas px, and the distance placement keeps between clusters. 250 by default; room_status reports it, and list_mentions, wait_for_mention, show_room, read_scene near and snapshot_scene near use it when they are given no radius of their own.",
+  "minimum": 0,
+  "type": "number"
+}
  3. First observedv0.1.0

TDQS

A3.7/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden and does disclose meaningful behavior: it loads the scene from a connected peer or from the persisted copy, and it states that the handle is returned. However, it does not cover potential failure modes (invalid link, nonexistent room), authentication/permissions, or what happens to the participant's presence after joining.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loads the key operation. It gives the who/what/how and a brief mention of the result, with no waste. The phrase 'where this server took' is a little redundant after 'result states the handle,' but overall it remains economized.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with 6 parameters and no output schema, the description covers the core join-and-load scenario well, but it does not explain the return shape fully, how to detect failure (e.g., invalid link, room not found), or how this tool relates to the complementary room-management siblings like open_room or create_room. There is room for more context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents every parameter. The description adds slight semantic value by indicating that the 'handle' parameter's resulting uniqueness is reflected in the result, but it mostly relies on the schema. Baseline for full coverage is 3; the added clarification pushes it slightly higher.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('Join'), a specific resource ('existing excalidraw.com live-collaboration room'), and a specific input ('from its link'), so an agent can tell this is the join-existing-room-by-link tool. It doesn't explicitly contrast with create_room or open_room, but the opening phrase makes the distinction evident.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description clearly conveys the intended use case: you have a live-collaboration link and want to join that existing room. It does not explicitly say 'do not use this to create a room' or name alternatives such as open_room or create_room, so it lacks explicit exclusions, but the when-to-use context is nevertheless clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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