create_or_update_note

THE RISK

Medium Risk

Why create_or_update_note needs a policy

This tool modifies persistent data in TheBrain's knowledge management system by creating new notes or updating existing ones. While reversible (notes are not permanently destroyed), it changes the state of the system. It does not execute arbitrary code, delete data irreversibly, or move money, making Write the appropriate category.

From the tool's definition Tool name 'create_or_update_note' and description 'Create or update a note with markdown content' explicitly indicates creating or modifying data. The verb 'create_or_update' is reversible—notes can be edited or deleted afterward.

Documented attack patterns abuse exactly the kind of access create_or_update_note gives an agent:

POLICY

How to control create_or_update_note

PolicyLayer is an MCP gateway — it sits between your AI agents and TheBrain MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for create_or_update_note:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_or_update_note": {
      "limits": [
        {
          "counter": "create_or_update_note_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

create_or_update_note 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.

Create a free account and register TheBrain MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More TheBrain MCP Server tools

Destructive delete_attachment Delete an attachment Destructive delete_link Delete a link Destructive delete_thought Delete a thought Write append_to_note Append content to an existing note Write add_file_attachment Add a file attachment (including images) to a thought Write add_url_attachment Add a URL attachment to a thought Write create_link Create a link between two thoughts with visual properties Write create_thought Create a new thought with optional visual properties

All 26 TheBrain MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about create_or_update_note

What does the create_or_update_note tool do? +

Create or update a note with markdown content. It is categorised as a Write tool in the TheBrain MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_or_update_note? +

Register the TheBrain MCP Server MCP server in PolicyLayer and add a rule for create_or_update_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 TheBrain MCP Server. Nothing to install.

What risk level is create_or_update_note? +

create_or_update_note is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit create_or_update_note? +

Yes. Add a rate_limit block to the create_or_update_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.

How do I block create_or_update_note completely? +

Set action: deny in the PolicyLayer policy for create_or_update_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.

What MCP server provides create_or_update_note? +

create_or_update_note is provided by the TheBrain MCP Server MCP server (redmorestudio/thebrain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every TheBrain MCP Server tool call.

Start from TheBrain MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →