Add a new phone number to the SMS list using a specific keyword ID. The keyword_id ties the subscription to an existing documented consent flow (required for TCPA/CTIA compliance). Returns the created subscriber.
AI agents use add_subscriber to create or update resources in Postscript — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Postscript environment.
This tool creates a new data record (adds a subscriber) in the SMS marketing platform, which is a Write operation. It modifies the state of the system by enrolling a new phone number.
From the tool's definition Tool description states it will 'Add a new phone number to the SMS list' and 'Returns the created subscriber', indicating reversible creation of a new record in the subscriber database.
Attacks that exploit this kind of access
Add a new phone number to the SMS list using a specific keyword ID. The keyword_id ties the subscription to an existing documented consent flow (required for TCPA/CTIA compliance). Returns the created subscriber. It is categorised as a Write tool in the Postscript MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Postscript MCP server in PolicyLayer and add a rule for add_subscriber: 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 Postscript. Nothing to install.
add_subscriber 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_subscriber 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_subscriber. 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_subscriber is provided by the Postscript MCP server (nobanks/postscript-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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