Update elements on a canvas. Requires room_id from a previous Canvs tool result. Pass elements array with id and fields to update. IMPORTANT: in each update object ONLY id is required; all other fields are optional patch fields. Include ONLY elements that need changes; elements omitted from the r...
Risk signalsHigh parameter count (19 properties)
Part of the Canvs server.
Free to start. No card required.
AI agents use update_elements to create or modify resources in Canvs. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call update_elements repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Canvs.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"update_elements": {
"limits": [
{
"counter": "update_elements_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Canvs policy for all 6 tools.
These attack patterns abuse exactly the kind of access update_elements gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Update elements on a canvas. Requires room_id from a previous Canvs tool result. Pass elements array with id and fields to update. IMPORTANT: in each update object ONLY id is required; all other fields are optional patch fields. Include ONLY elements that need changes; elements omitted from the request remain unchanged on the board. Prefer this tool for SMALL edits to existing diagrams (rename/move/restyle a few elements), typically after query_elements.. It is categorised as a Write tool in the Canvs MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Canvs MCP server in PolicyLayer and add a rule for update_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 Canvs. Nothing to install.
update_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 update_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 update_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.
update_elements is provided by the Canvs MCP server (https://app.canvs.io/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 6 Canvs tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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