create_link

THE RISK

Medium Risk

Why create_link needs a policy

Creating links in a knowledge management system modifies data structure reversibly by establishing connections between thoughts. This is a Write operation—it creates new metadata/relationships without deleting data, executing external code, or causing irreversible changes. The presence of delete_link on the same server confirms reversibility.

From the tool's definition Tool name 'create_link' and description indicate it creates a relationship between existing thoughts. This is a reversible modification operation (links can be deleted via 'delete_link' tool present on the server), with no destructive capability and no access…

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

POLICY

How to control create_link

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_link:

policy.json

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

create_link 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_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 create_link

What does the create_link tool do? +

Create a link between two thoughts with visual properties. 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_link? +

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

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

Can I rate-limit create_link? +

Yes. Add a rate_limit block to the create_link 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_link completely? +

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

create_link 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 →