AI agents use unlock_elements to create or update resources in Excalidraw MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Excalidraw MCP Server environment.
The tool modifies element properties (lock state) to enable subsequent edits, which is a Write operation. Severity is low because: (1) the change is easily reversible by re-locking, (2) Excalidraw diagrams are typically ephemeral design artifacts with no permanent consequences, (3) no data destruction occurs, and (4) the blast radius is limited to unlocking visual elements in a diagram.
From the tool's definition unlock_elements changes element state from locked to unlocked, enabling modification. This is a reversible state change that affects only element properties, not data deletion or financial operations.
Documented attack patterns abuse exactly the kind of access unlock_elements 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 unlock_elements:
{
"version": "1",
"default": "deny",
"tools": {
"unlock_elements": {
"limits": [
{
"counter": "unlock_elements_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}unlock_elements stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Unlock elements to allow modification. It is categorised as a Write tool in the Excalidraw MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Excalidraw MCP Server MCP server in PolicyLayer and add a rule for unlock_elements: 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.
unlock_elements is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the unlock_elements 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 unlock_elements. 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.
unlock_elements 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.