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damientilman

Mailchimp MCP

add_member

Add a new contact to a Mailchimp audience. Provide email address and list ID; optionally include name and tags. Returns member details or error if already present.

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?

Despite no annotations, the description covers side effects (opt-in email), authentication (API key), rate limits (max 10 concurrent requests), and respect for read-only/dry-run modes. It also mentions the 'Member Exists' error.

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 separate sections for usage, side effects, limitations, and parameters. Every sentence adds value without redundancy. Front-loaded with purpose and guidelines.

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?

Covers input, output (return fields despite output schema), error conditions, authentication, rate limits, side effects, and guidance on sibling tools. Complete for a mutation tool.

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 the description provides detailed explanations for each parameter: list_id format and how to obtain, email_address uniqueness constraint, status options with defaults, first/last name as merge fields, tags as comma-separated. Adds significant meaning.

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 'Add a new member to an audience with optional name and tags.' The verb 'add' and resource 'member to an audience' are specific. It distinguishes from sibling tools by referencing update_member, tag_member, etc.

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 guides when to use this tool vs alternatives: 'Choose the right member tool: add_member for new contacts, update_member to change profile/status...' Also notes the side effect of pending status 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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