substack_append_to_draft · Substack MCP Server MCP

WHAT IT DOES

What substack_append_to_draft does on Substack MCP Server

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

WHY IT NEEDS A POLICY

Why substack_append_to_draft needs a policy

This tool modifies existing data (draft posts) by appending content, which is characteristic of Write category operations. It is reversible—appended content can be edited or removed.

From the tool's definition Tool appends content to an existing draft, a reversible modification operation. Description explicitly states it's used for 'live blogging,' indicating dynamic content updates to draft posts.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

substack_append_to_draft Rate-limited

substack_append_to_draft 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": {
    "substack_append_to_draft": {
      "limits": [
        {
          "counter": "substack_append_to_draft_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 Substack MCP Server, so you can run agents against it safely.

FAQ

Questions about substack_append_to_draft

What does the substack_append_to_draft tool do? +

Append content to an existing draft (for live blogging). It is categorised as a Write tool in the Substack MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on substack_append_to_draft? +

Register the Substack MCP Server MCP server in PolicyLayer and add a rule for substack_append_to_draft: 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 Server. Nothing to install.

What risk level is substack_append_to_draft? +

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

Can I rate-limit substack_append_to_draft? +

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

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

substack_append_to_draft is provided by the Substack MCP Server MCP server (jessicaruthabbott/my-substack-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.