substack_publish · Substack MCP Server MCP: Risk & Policy

WHAT IT DOES

What substack_publish does on Substack MCP Server

AI agents use substack_publish 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_publish needs a policy

This tool creates new published content on the Substack platform, which is a reversible modification (posts can be unpublished or deleted). It does not permanently destroy data nor move money, so it falls under Write rather than Destructive or Financial. Severity is high because publishing can reach an audience immediately and unauthorized publication could damage reputation or expose sensitive information.

From the tool's definition Tool name 'substack_publish' and description 'Publish a draft to your Substack' indicate the tool creates/modifies published content by converting a draft into a live post.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

substack_publish Rate-limited

substack_publish 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_publish": {
      "limits": [
        {
          "counter": "substack_publish_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_publish

What does the substack_publish tool do? +

Publish a draft to your Substack. 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_publish? +

Register the Substack MCP Server MCP server in PolicyLayer and add a rule for substack_publish: 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_publish? +

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

Can I rate-limit substack_publish? +

Yes. Add a rate_limit block to the substack_publish 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_publish completely? +

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

substack_publish 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.