trello_add_attachment · Mtl Trello MCP: Risk & Policy

WHAT IT DOES

What trello_add_attachment does on Mtl Trello

AI agents use trello_add_attachment to create or update resources in Mtl Trello — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mtl Trello environment.

WHY IT NEEDS A POLICY

Why trello_add_attachment needs a policy

Attaching files to cards is a data modification that persists but is reversible (attachments can be removed). This is Write-category behavior. Severity is medium because while the operation modifies shared team data and could introduce unwanted files to a collaborative board, attachments are easily removable and do not cause irreversible harm like deletion would.

From the tool's definition Tool description states 'Attach a local file...to a Trello card' — this creates/modifies card data by adding an attachment, a reversible operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

trello_add_attachment Rate-limited

trello_add_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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Mtl Trello, so you can run agents against it safely.

FAQ

Questions about trello_add_attachment

What does the trello_add_attachment tool do? +

Attach a local file (image, PDF, etc.) to a Trello card. It is categorised as a Write tool in the Mtl Trello MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on trello_add_attachment? +

Register the Mtl Trello MCP server in PolicyLayer and add a rule for trello_add_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 Mtl Trello. Nothing to install.

What risk level is trello_add_attachment? +

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

Can I rate-limit trello_add_attachment? +

Yes. Add a rate_limit block to the trello_add_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 trello_add_attachment completely? +

Set action: deny in the PolicyLayer policy for trello_add_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 trello_add_attachment? +

trello_add_attachment is provided by the Mtl Trello MCP server (musictechlab/mtl-trello-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.