Create an internal note on a thread (not visible to customer)
AI agents use create_note to create or update resources in Plain Com MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Plain Com MCP Server environment.
An AI agent can call create_note faster than any human can review — one bad instruction and it creates or modifies resources in Plain Com MCP Server by the hundred, each call as confident as the last.
Attacks that exploit this kind of access
Create an internal note on a thread (not visible to customer). It is categorised as a Write tool in the Plain Com MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Plain Com MCP Server MCP server in PolicyLayer and add a rule for create_note: 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 Plain Com MCP Server. Nothing to install.
create_note 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 create_note 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 create_note. 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.
create_note is provided by the Plain Com MCP Server MCP server (tellahq/plain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.