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damientilman

Mailchimp MCP

batch_subscribe

Add or update up to 500 members in one request. Use for bulk operations; pending members receive a double opt-in email.

Instructions

Add or update up to 500 members in a single synchronous request.

Use for bulk operations. Choose the right member tool: batch_subscribe for 2-500 members, add_member or update_member for a single member, create_batch for imports larger than 500. Side effect: members with status='pending' each receive 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. members_json: JSON array of members (max 500). Each requires email_address and status ('subscribed'/'unsubscribed'/'cleaned'/'pending'). Optional: merge_fields, tags. update_existing: If true (default), existing members are updated. If false, skipped as errors.

Returns: JSON with new_members, updated_members, errors array, total_created, total_updated, error_count.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
list_idYes
members_jsonYes
update_existingNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior5/5

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

With no annotations, the description fully covers behavioral traits: side effect of double opt-in email for pending members, authentication via API key, concurrency limit of 10, 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?

The description is well-structured with clear sections. It starts with the primary action and scope, then provides usage guidance, side effects, and parameter details. Every sentence adds value without unnecessary words.

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 lack of annotations and the presence of an output schema, the description covers all necessary aspects: parameters, constraints, side effects, return format, and limitations. It is complete for the tool's complexity.

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 adds significant meaning: list_id format and source, members_json structure and constraints, update_existing behavior and default value. This compensates entirely for the missing schema descriptions.

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 adds or updates up to 500 members synchronously, specifying the verb and resource. It distinguishes from siblings by naming alternatives for different member counts.

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?

It explicitly says to use for bulk operations of 2-500 members, and advises using add_member/update_member for single members and create_batch for larger imports. This provides clear context and alternatives.

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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