List all newsletters you
AI agents call list_subscriptions to retrieve information from Substack Reader MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves information about the user's newsletter subscriptions without modifying, creating, or deleting any data. It is a read-only operation that queries existing subscription data. The low severity reflects that exposure of subscription lists poses minimal risk compared to write or destructive operations, though it does reveal user subscription preferences.
From the tool's definition Tool name 'list_subscriptions' and description 'List all newsletters you' indicate a retrieval/query operation with no side effects.
Attacks that exploit this kind of access
List all newsletters you. It is categorised as a Read tool in the Substack Reader MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Substack Reader MCP Server MCP server in PolicyLayer and add a rule for list_subscriptions: 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 Substack Reader MCP Server. Nothing to install.
list_subscriptions is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_subscriptions 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 list_subscriptions. 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.
list_subscriptions is provided by the Substack Reader MCP Server MCP server (kealu-inc/substack-reader-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.
Teams ship this data inside their own products. See what a licence covers →