upload_attachment · Redmine MCP: Risk & Policy | PolicyLayer

WHAT IT DOES

What upload_attachment does on Redmine

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

WHY IT NEEDS A POLICY

Why upload_attachment needs a policy

The tool uploads files to Redmine, which is a Write operation as it creates new attachment data. It is reversible (attachments can be removed), so it does not qualify as Destructive. Severity is medium because file uploads could introduce malicious content or consume storage resources, but the operation itself is not irreversible and does not directly execute code or move money.

From the tool's definition Tool description states 'Upload a file to Redmine and get a token' and 'when creating/updating issues or wiki pages to attach the file', indicating it creates/modifies data reversibly by attaching files to Redmine resources.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

upload_attachment Rate-limited

upload_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": {
    "upload_attachment": {
      "limits": [
        {
          "counter": "upload_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 Redmine, so you can run agents against it safely.

FAQ

Questions about upload_attachment

What does the upload_attachment tool do? +

Upload a file to Redmine and get a token. Use the token when creating/updating issues or wiki pages to attach the file. It is categorised as a Write tool in the Redmine MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on upload_attachment? +

Register the Redmine MCP server in PolicyLayer and add a rule for upload_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 Redmine. Nothing to install.

What risk level is upload_attachment? +

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

Can I rate-limit upload_attachment? +

Yes. Add a rate_limit block to the upload_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 upload_attachment completely? +

Set action: deny in the PolicyLayer policy for upload_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 upload_attachment? +

upload_attachment is provided by the Redmine MCP server (yenpu/redmine-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.