append_to_note_tool
AI agents use append_to_note_tool to create or update resources in Brain — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Brain environment.
The tool name strongly suggests appending (adding) content to an existing Markdown note, which is a reversible write operation. The description is empty, reducing confidence, but the naming convention and server context (read/write tools for Markdown notes) support this classification. Severity is medium since it modifies personal notes data but is not irreversible.
From the tool's definition Tool name: 'append_to_note_tool' — 'append' implies adding content to an existing note; sibling tools confirm a read/write notes system
Documented attack patterns abuse exactly the kind of access append_to_note_tool gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Brain, and nothing reaches the server without passing your rules. This is the rule we recommend for append_to_note_tool:
{
"version": "1",
"default": "deny",
"tools": {
"append_to_note_tool": {
"limits": [
{
"counter": "append_to_note_tool_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}append_to_note_tool 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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append_to_note_tool. It is categorised as a Write tool in the Brain MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Brain MCP server in PolicyLayer and add a rule for append_to_note_tool: 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 Brain. Nothing to install.
append_to_note_tool 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 append_to_note_tool 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 append_to_note_tool. 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.
append_to_note_tool is provided by the Brain MCP server (irahulstomar/brain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Brain, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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10 Brain tools catalogued and risk-classified — across an index of 43,000+ MCP servers.