Get an AI-readable description of the current canvas: element types, positions, connections, labels, spatial layout, and bounding box. Use this to understand what is on the canvas before making changes.
AI agents call describe_scene to retrieve information from Excalidraw MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The describe_scene tool only retrieves and queries the current state of a diagram canvas. It performs no modifications, deletions, or external operations. It is a read-only operation that provides context for understanding diagram contents, making it a Read category tool with low severity since misuse would only result in retrieving diagram metadata without causing harm.
From the tool's definition Tool description explicitly states it 'Get[s] an AI-readable description' of the canvas, providing element types, positions, connections, labels, and spatial layout.
Documented attack patterns abuse exactly the kind of access describe_scene gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Excalidraw MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for describe_scene:
{
"version": "1",
"default": "deny",
"tools": {
"describe_scene": {}
}
}describe_scene is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Get an AI-readable description of the current canvas: element types, positions, connections, labels, spatial layout, and bounding box. Use this to understand what is on the canvas before making changes. It is categorised as a Read tool in the Excalidraw MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Excalidraw MCP Server MCP server in PolicyLayer and add a rule for describe_scene: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Excalidraw MCP Server. Nothing to install.
describe_scene is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the describe_scene rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for describe_scene. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
describe_scene is provided by the Excalidraw MCP Server MCP server (yctimlin/mcp_excalidraw). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 26 Excalidraw MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
26 Excalidraw MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.