get_subscriber_count

THE RISK

Low Risk

Why get_subscriber_count needs a policy

This tool queries subscriber count data but does not create, modify, delete, execute code, or commit financial transactions. It is a read-only operation that retrieves metrics about the publication's audience. The blast radius is minimal; misuse would only expose already-public subscription statistics.

From the tool's definition Tool name is 'get_subscriber_count' and description states it 'Get[s] the total number of subscribers' — a pure retrieval operation with no side effects.

Documented attack patterns abuse exactly the kind of access get_subscriber_count gives an agent:

POLICY

How to control get_subscriber_count

PolicyLayer is an MCP gateway — it sits between your AI agents and Substack Mcp Plus, and nothing reaches the server without passing your rules. This is the rule we recommend for get_subscriber_count:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "get_subscriber_count": {}
  }
}

get_subscriber_count is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Substack Mcp Plus — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

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EXPLORE

Related tools and policies

More Substack Mcp Plus tools

Destructive delete_draft Delete a draft post. IMPORTANT: You MUST ALWAYS ask the user to confirm deletion in a foll Execute publish_post Publish a draft post immediately to your Substack publication. This makes the post publicl Write create_formatted_post Create a new formatted draft post on Substack. Supports full markdown formatting. IMPORTAN Write duplicate_post Create a copy of an existing post as a new draft. Perfect for using posts as templates. IM Write update_post Update an existing Substack draft post. WARNING: This tool COMPLETELY REPLACES the specifi Write upload_image Upload an image file from your local computer to Substack Read get_post_content Read the full content of a specific post (draft or published) with all its formatting. Ret Read get_sections Get a list of available sections/categories in your Substack publication. Sections help or

All 12 Substack Mcp Plus tools →

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about get_subscriber_count

What does the get_subscriber_count tool do? +

Get the total number of subscribers to your Substack publication. Useful for tracking growth and understanding your audience size. It is categorised as a Read tool in the Substack Mcp Plus MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get_subscriber_count? +

Register the Substack Mcp Plus MCP server in PolicyLayer and add a rule for get_subscriber_count: 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 Mcp Plus. Nothing to install.

What risk level is get_subscriber_count? +

get_subscriber_count is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit get_subscriber_count? +

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

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

get_subscriber_count is provided by the Substack Mcp Plus MCP server (ty13r/substack-mcp-plus). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Substack Mcp Plus tool call.

Start from Substack Mcp Plus, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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