Mailchimp MCP Server

mailchimp_merge_fields_update

Update an existing merge field in a Mailchimp audience by specifying the list ID and merge field ID, with optional changes to tag, name, visibility, required status, and other attributes.

Instructions

Update an existing merge field

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": {
      "list_id": "<list_id>",
      "merge_id": "<merge_id>"
    },
    "name": "mailchimp_merge_fields_update"
  }
}

Input Schema

Name	Required	Description
`tag`	No	Updated merge tag
`name`	No	Updated display name
`public`	No	Updated public visibility
`list_id`	Yes	List/audience ID
`options`	No	Updated field options
`merge_id`	Yes	Merge field ID
`required`	No	Updated required status
`help_text`	No	Updated help text
`default_value`	No	Updated default value
`display_order`	No	Updated display order

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 2, 2026

TDQS

B3.4/5.0

Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It only states the update action but omits any details about side effects, partial update semantics, required permissions, or how it interacts with existing subscriber data. This is a significant gap for a mutation tool.

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 a single, focused sentence that immediately communicates the tool's purpose without extraneous information. It is well structured and easy to parse, earning full marks for conciseness.

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?

Despite having 10 parameters and a nested object, the description is extremely sparse. It does not mention required parameters, update semantics, or expected outcomes. With no annotations or output schema, the description is insufficient to fully guide an agent on how to invoke and interpret the tool correctly.

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?

The input schema provides comprehensive descriptions for all parameters, achieving 100% coverage. The tool description adds no parameter information beyond the schema, so a baseline score of 3 is appropriate. It neither enriches nor detracts 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 action ('Update') and the resource ('existing merge field'), which is specific and unambiguous. It effectively distinguishes this tool from its sibling operations like create, delete, get, and list for merge fields.

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

Usage Guidelines3/5

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

The description implies usage: use this tool when you need to modify an existing merge field. However, it provides no explicit guidance on when to choose this over alternatives, nor any exclusions or prerequisites. The context is clear only through the tool name.

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

Deploy Server