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Remove subscriber

remove_subscriber

Destructive

Removes an email from your Substack subscriber list, stopping future emails and canceling any paid subscription with a refund for the unused portion.

Instructions

Remove one email from your subscriber list.

Removes a subscriber from your list, as Remove in the subscriber's menu does: they get no more emails from you and no notice. A paid subscription is cancelled and Substack refunds the unused part. An email not on your list returns an error; add_subscriber takes about a minute before the address is listed.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "email": "<email>"
    },
    "name": "remove_subscriber"
  }
}

Input Schema

Name	Required	Description	Default
`email`	Yes	Subscriber's email address.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 24, 2026

TDQS

A4.3/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations, which only say destructive, non-idempotent, and open-world. The description discloses the user-visible consequence (no notice sent), the billing consequence (paid subscription cancelled with a prorated refund from Substack), and the failure mode (error on unknown email). That is exactly the side-effect detail an agent needs before invoking a destructive tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the action, then layered with consequences, error behavior, and a timing caveat — every sentence contributes. The first two clauses partially restate the same removal act ('Remove one email…' / 'Removes a subscriber…'), a small redundancy that keeps it short of a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter destructive mutation with no output schema, the description covers side effects, refunds, error behavior, and a race condition with add_subscriber. It stops short of saying whether removal is reversible or can be re-added, which is the remaining question an agent might have before a destructive call.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is a single required parameter and the schema documents it fully at 100% coverage, so the baseline of 3 applies. The description's 'one email' phrasing confirms cardinality and that the address must already be on the list, but adds no format or normalization guidance beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Remove one email from your subscriber list') with an explicit scope of one address, and the follow-up sentence anchors it to the concrete UI action ('as Remove in the subscriber's menu does'). An agent can immediately distinguish this from sibling list_subscribers, add_subscriber, and tag_subscribers.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives the operative condition: an address not on the list returns an error, and warns that add_subscriber takes about a minute before the address is listed, which implies you must wait before removal succeeds. It does not explicitly name a preferred alternative or state exclusions, but no sibling performs removal, so the routing gap is minor.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.