@kieksme/listmonk-mcp

Create Subscriber

listmonk_create_subscriber

Creates a new subscriber with email, name, status, and custom attributes, optionally subscribing them to one or more lists immediately.

Instructions

Creates a new subscriber, optionally subscribing them to one or more lists immediately.

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": "<name>"
    },
    "name": "listmonk_create_subscriber"
  }
}

Input Schema

Name	Required	Description	Default
`name`	Yes
`email`	Yes
`lists`	No	List ids to subscribe to.
`status`	No		enabled
`attribs`	No	Arbitrary custom attributes as a JSON object.
`list_uuids`	No
`response_format`	No	Output format: 'markdown' for human-readable text (default) or 'json' for machine-readable data.	markdown
`preconfirm_subscriptions`	No	Mark list subscriptions as confirmed immediately.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.3.0Nov 4, 2026

TDQS

C2.9/5.0

Behavior3/5

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

Annotations already declare a mutating, non-idempotent, non-destructive, open-world operation, so the safety profile is covered. The description adds the notable side effect that list subscriptions can be created immediately, but omits what happens on duplicate email, whether confirmation emails are sent, or how status interacts with subscription confirmation.

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?

A single front-loaded sentence with no filler and the key behavior (list subscription) placed where it is read first. It is efficient, though the terseness contributes to the coverage gaps elsewhere.

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

Completeness2/5

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

For an 8-parameter mutation tool with nested objects, two enums, no output schema, and no idempotency guidance, the description is far too thin. An agent would have to guess at duplicate handling, confirmation flows, and the meaning of half the parameters.

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

Parameters2/5

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

With 8 parameters at 50% schema description coverage, the description only gestures at the 'lists' parameter ('subscribing them to one or more lists'). It says nothing about status, attribs, list_uuids, response_format, or preconfirm_subscriptions, leaving ambiguities such as lists vs list_uuids unresolved.

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

Purpose4/5

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

The description names a specific verb and resource ('Creates a new subscriber') and adds a scope note about optional immediate list subscription. It is clear, though it offers no differentiation from related siblings like listmonk_import_subscribers or listmonk_update_subscriber.

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

Usage Guidelines2/5

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

There is no explicit when-to-use guidance: nothing says whether to prefer this over listmonk_import_subscribers for bulk adds, over listmonk_update_subscriber for existing contacts, or how it behaves when the email already exists. Usage is only implied by the verb 'Creates'.

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

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