Add a phone number to the opt-out list (suppresses future messages)
AI agents use add_opt_out to create or update resources in Mcp Ap2 — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mcp Ap2 environment.
This tool creates a new record (phone number entry) on an opt-out/suppression list, which is a reversible data modification. It does not delete data (Destructive), execute arbitrary code (Execute), transfer funds (Financial), or merely read data (Read).
From the tool's definition Tool name 'add_opt_out' and description 'Add a phone number to the opt-out list (suppresses future messages)' indicates a modification operation that creates or updates suppression list entries.
Documented attack patterns abuse exactly the kind of access add_opt_out gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for add_opt_out:
{
"version": "1",
"default": "deny",
"tools": {
"add_opt_out": {
"limits": [
{
"counter": "add_opt_out_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_opt_out 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.
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Add a phone number to the opt-out list (suppresses future messages). It is categorised as a Write tool in the Mcp Ap2 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for add_opt_out: 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 Mcp Ap2. Nothing to install.
add_opt_out is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add_opt_out 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.
Set action: deny in the PolicyLayer policy for add_opt_out. 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.
add_opt_out is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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