add_file_attachment

THE RISK

Medium Risk

Why add_file_attachment needs a policy

This tool creates or modifies data (attaches files to thoughts) without permanently destroying information. It is reversible via delete_attachment, making it a Write operation rather than Destructive. The severity is medium because an AI agent could attach malicious, sensitive, or unwanted files to thoughts in a knowledge management system, but the impact is confined to that system and attachments can be removed.

From the tool's definition Tool name 'add_file_attachment' and description 'Add a file attachment (including images) to a thought' indicate file attachment creation/modification. Related tool 'delete_attachment' confirms write/destructive operations exist on this server.

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

POLICY

How to control add_file_attachment

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 add_file_attachment:

policy.json

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

add_file_attachment 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_url_attachment Add a URL attachment to a thought Write create_link Create a link between two thoughts with visual properties Write create_or_update_note Create or update a note with markdown content 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 add_file_attachment

What does the add_file_attachment tool do? +

Add a file attachment (including images) to a thought. 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 add_file_attachment? +

Register the TheBrain MCP Server MCP server in PolicyLayer and add a rule for add_file_attachment: 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 add_file_attachment? +

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

Can I rate-limit add_file_attachment? +

Yes. Add a rate_limit block to the add_file_attachment 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 add_file_attachment completely? +

Set action: deny in the PolicyLayer policy for add_file_attachment. 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 add_file_attachment? +

add_file_attachment 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 →