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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; returns error if duplicate. Use 'pending' status for double opt-in.

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.

Authenticated via API key. Max 10 concurrent requests. Respects read-only and dry-run modes.

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
list_idYes
email_addressYes
statusNosubscribed
first_nameNo
last_nameNo
tagsNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior5/5

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

No annotations provided, but description fully covers behavior: returns 'Member Exists' error, triggers double opt-in email, authentication info, rate limits, and respect for read-only/dry-run modes.

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?

Description is well-structured with a brief purpose, clear usage guidelines, behavioral details, and parameter list. Front-loaded with core purpose, no waste.

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 complexity and no annotations, description covers purpose, parameters, behavior, error handling, and return format. Differentiates from many sibling tools explicitly.

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 coverage is 0%, but description includes detailed Args section explaining each parameter's format, constraints, and how to obtain list_id. This adds significant meaning beyond schema titles and 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?

Clearly states it adds a new member to an audience, creates a new contact, and distinguishes from sibling tools like update_member and batch_subscribe.

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?

Explicitly lists when to use this tool vs alternatives (e.g., add_member for new, update_member for existing, batch_subscribe for bulk). Also explains side effect of status='pending' triggering opt-in email.

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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