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damientilman

Mailchimp MCP

batch_subscribe

Add or update up to 500 members in one synchronous request. Handles bulk operations with double opt-in for pending members.

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.

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
accountNo
list_idYes
members_jsonYes
update_existingNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

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

Annotations indicate write operation (readOnlyHint=false) and non-destructive. Description adds crucial behavioral detail: side effect of sending double opt-in email for pending members. Does not mention rate limits or auth requirements, but covers key trait 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?

Three clearly structured paragraphs: summary, usage guidelines with side effect, then parameter descriptions. No unnecessary words, every sentence adds value.

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 output schema exists, description covers purpose, usage, parameters, side effect, and return values. Complete for the tool's complexity with 4 parameters and existing output schema.

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

Parameters4/5

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

Input schema has 0% description coverage. Description compensates by explaining list_id format and source, members_json structure and limits, update_existing behavior. Does not explain 'account' parameter, but overall 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?

Description clearly states the tool adds or updates up to 500 members synchronously. It distinguishes from siblings by specifying batch_subscribe is for 2-500 members, add_member/update_member for single, and create_batch for larger imports.

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 tells when to use: bulk operations. Provides alternatives: add_member/update_member for single, create_batch for >500. Clear context for 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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