Update existing shapes by id. Provide partial props to change.
AI agents use update_shape to create or update resources in Tl Draw — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Tl Draw environment.
update_shape modifies existing canvas objects in a way that can be undone or changed again. It does not delete data (which would be Destructive), execute arbitrary code (Execute), cause financial impact (Financial), or merely read data (Read). The severity is low because the blast radius of misusing this tool is limited to modifications within a tldraw canvas visualization, which are non-critical assets.
From the tool's definition Tool description states 'Update existing shapes by id. Provide partial props to change.' — this is a reversible modification operation.
Documented attack patterns abuse exactly the kind of access update_shape gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Tl Draw, and nothing reaches the server without passing your rules. This is the rule we recommend for update_shape:
{
"version": "1",
"default": "deny",
"tools": {
"update_shape": {
"limits": [
{
"counter": "update_shape_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_shape 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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Update existing shapes by id. Provide partial props to change. It is categorised as a Write tool in the Tl Draw MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Tl Draw MCP server in PolicyLayer and add a rule for update_shape: 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 Tl Draw. Nothing to install.
update_shape 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 update_shape 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 update_shape. 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.
update_shape is provided by the Tl Draw MCP server (siddharth11roy/tldraw-claude-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Tl Draw, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
4 Tl Draw tools catalogued and risk-classified — across an index of 43,000+ MCP servers.