mailosaur_servers_update · Mailosaur MCP: Risk & Policy

WHAT IT DOES

What mailosaur_servers_update does on Mailosaur MCP

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

WHY IT NEEDS A POLICY

Why mailosaur_servers_update needs a policy

This tool modifies server settings/configuration in a reversible manner (updates rather than deletes). It is classified as Write rather than Execute because it changes data state rather than running arbitrary code or external operations. Severity is medium because misconfiguration could affect email/SMS testing services and potentially disrupt workflows, but changes are reversible through subsequent updates.

From the tool's definition Tool name 'mailosaur_servers_update' and description 'Update a Mailosaur server' indicate modification of server configuration data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mailosaur_servers_update Rate-limited

mailosaur_servers_update 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": {
    "mailosaur_servers_update": {
      "limits": [
        {
          "counter": "mailosaur_servers_update_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 Mailosaur MCP, so you can run agents against it safely.

FAQ

Questions about mailosaur_servers_update

What does the mailosaur_servers_update tool do? +

Update a Mailosaur server. It is categorised as a Write tool in the Mailosaur MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on mailosaur_servers_update? +

Register the Mailosaur MCP server in PolicyLayer and add a rule for mailosaur_servers_update: 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 Mailosaur MCP. Nothing to install.

What risk level is mailosaur_servers_update? +

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

Can I rate-limit mailosaur_servers_update? +

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

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

mailosaur_servers_update is provided by the Mailosaur MCP server (mrnewdelhi/mailosaur-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.