AI agents use attach-rubric-to-assignment to create or update resources in Canvas MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Canvas MCP Server environment.
This tool modifies assignment metadata by attaching a rubric, which constitutes a Write operation—data is being created or changed. The action is reversible (a rubric can be detached or replaced), so it does not qualify as Destructive.
From the tool's definition Tool attaches (modifies) a rubric to an assignment, which is a reversible data modification operation. The description states 'Attach a rubric to an assignment,' indicating the tool creates or modifies the association between a rubric and assignment resource.
Documented attack patterns abuse exactly the kind of access attach-rubric-to-assignment gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Canvas MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for attach-rubric-to-assignment:
{
"version": "1",
"default": "deny",
"tools": {
"attach-rubric-to-assignment": {
"limits": [
{
"counter": "attach-rubric-to-assignment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}attach-rubric-to-assignment 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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Attach a rubric to an assignment. It is categorised as a Write tool in the Canvas MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Canvas MCP Server MCP server in PolicyLayer and add a rule for attach-rubric-to-assignment: 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 Canvas MCP Server. Nothing to install.
attach-rubric-to-assignment 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 attach-rubric-to-assignment 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 attach-rubric-to-assignment. 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.
attach-rubric-to-assignment is provided by the Canvas MCP Server MCP server (r-huijts/canvas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Canvas MCP Server, 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.
50 Canvas MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.