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damientilman

Mailchimp MCP

add_member

Add a new member to a Mailchimp audience with optional name and tags. Creates a contact and returns error if the email already exists.

Instructions

Add a new member to an audience with optional name and tags.

Creates a new contact. Returns "Member Exists" error if already present. Choose the right member tool: add_member for new contacts, update_member to change profile/status of existing contacts, tag_member to manage tags on existing contacts, batch_subscribe for bulk add/update (up to 500), unsubscribe_member to opt out, delete_member for permanent GDPR removal. Side effect: status='pending' triggers a double opt-in confirmation email.

Args: list_id: Audience/list ID (10-char alphanumeric, e.g. 'abc123def4'). Obtain from list_audiences. email_address: Email of the new member. Must not already exist in the audience. status: 'subscribed' (default), 'pending' (triggers opt-in email), 'unsubscribed', 'cleaned'. first_name: First name (FNAME merge field). last_name: Last name (LNAME merge field). tags: Comma-separated tag names (e.g. 'VIP,Newsletter'). Created automatically if new.

Returns: JSON with id (MD5 hash of email), email_address, status, full_name.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
tagsNo
statusNosubscribed
accountNo
list_idYes
last_nameNo
first_nameNo
email_addressYes

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

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

Annotations (readOnlyHint=false, idempotentHint=false, destructiveHint=false) are consistent. The description adds valuable context: a side effect (status='pending' triggers double opt-in email) and an error condition ('Member Exists' if duplicate). It doesn't cover auth or rate limits, but the added details go beyond annotations.

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: a concise one-line summary, then an overview, a sibling tool comparison, a detailed Args section, and a Returns section. Every sentence contributes information without redundancy.

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

Completeness5/5

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

Given the tool has 7 parameters, 2 required, and an output schema, the description covers all essential aspects: purpose, usage, parameters, return values, errors, side effects, and sibling distinctions. No significant gaps remain.

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

Parameters5/5

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

Schema description coverage is 0%, but the description fully explains each parameter (list_id format, email requirement, status options with defaults, first/last name as merge fields, tags as comma-separated). This adds significant meaning beyond the raw schema types.

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 starts with a clear action ('Add a new member') and resource ('to an audience'), and explains it creates a new contact. It distinguishes from siblings like update_member, tag_member, etc., satisfying the specific verb+resource+differentiation criteria.

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 explicitly lists alternative tools (update_member, tag_member, batch_subscribe, unsubscribe_member, delete_member) and when to use each. This provides excellent guidance on choosing the right tool.

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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