Skip to main content
Glama
damientilman

Mailchimp MCP

create_merge_field

Add a custom merge field to your Mailchimp audience for storing extra member data beyond default fields like name and address.

Instructions

Create a new custom merge field in an audience for storing additional member data.

Use to add custom data fields beyond the defaults (FNAME, LNAME, ADDRESS, PHONE). Once created, populate per-member via add_member/update_member using the tag name. The type cannot be changed after creation. Use list_merge_fields to check existing fields first.

Args: list_id: The Mailchimp audience/list ID (e.g. 'abc123def4'). Obtain from list_audiences. name: Display name for the field (e.g. 'Company Name'). type: Field data type. Valid values: 'text', 'number', 'address', 'date', 'birthday', 'phone', 'url', 'imageurl', 'zip', 'dropdown', 'radio'. Cannot be changed after creation. tag: Short uppercase tag name (e.g. 'COMPANY'). Max 10 characters, letters and numbers only. Auto-generated from name if omitted. Used as |TAG| in email content. required: Whether the field is required when subscribing (default false). default_value: Default value for new subscribers. choices: Comma-separated choices for 'dropdown' or 'radio' types (e.g. 'Small,Medium,Large'). Required when type is 'dropdown' or 'radio'. Ignored for other types.

Returns: JSON with fields: merge_id (int, for update/delete), tag (string), name, type, required.

Example: create_merge_field(list_id="abc123", name="Company", type="text", tag="COMPANY") -> {"merge_id": 5, "tag": "COMPANY", "name": "Company", "type": "text", ...}

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
tagNo
nameYes
typeYes
accountNo
choicesNo
list_idYes
requiredNo
default_valueNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

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

Annotations are minimal (readOnlyHint false, etc.), so the description carries the burden. It discloses that the type cannot be changed after creation and that fields are populated via add_member/update_member. It does not cover all behavioral aspects like error handling or rate limits.

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

Conciseness5/5

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

The description is well-structured with a brief overview, a clear 'Args' section, a 'Returns' section, and an example. It is concise yet comprehensive, with no wasted words.

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?

The description is fairly complete, covering the purpose, parameters, return value, and linking to list_merge_fields. However, it does not mention the sibling delete_merge_field or handle potential error scenarios. The output is described despite the presence of an output schema.

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

Parameters4/5

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

Schema has 0% coverage, so the description compensates by explaining most parameters (list_id, name, type, tag, required, default_value, choices) including the relationship between choices and type. However, it misses the 'account' parameter from 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?

The description clearly states the tool's purpose: 'Create a new custom merge field in an audience for storing additional member data.' It distinguishes from sibling tools like list_merge_fields and update_merge_field by its specific verb and resource.

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

Usage Guidelines5/5

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

The description provides explicit usage guidance: 'Use to add custom data fields beyond the defaults' and advises using list_merge_fields to check existing fields first. It also mentions prerequisites like obtaining list_id from list_audiences.

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

Install Server

Other Tools

Latest Blog Posts

MCP directory API

We provide all the information about MCP servers via our MCP API.

curl -X GET 'https://glama.ai/api/mcp/v1/servers/damientilman/mailchimp-mcp-server'

If you have feedback or need assistance with the MCP directory API, please join our Discord server