Create contact lists to organize email recipients, with optional descriptions and double opt-in settings. Simplify audience segmentation and campaign targeting via EuroMail.
Create a contact list for organizing recipients.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | List name (max 255 characters) | |
| description | No | List description | |
| double_opt_in | No | Require double opt-in (default: false) |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure, but 'Create ... for organizing recipients' only implies a mutation. It fails to mention permission requirements, whether duplicate names are rejected, whether double_opt_in changes downstream sending behavior, or what the response returns (e.g., a new list ID that add_contacts would need).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single front-loaded sentence with zero filler, which is appropriate for a simple create tool. It is efficient but borders on under-specification rather than being genuinely complete.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a write operation with no annotations and no output schema, the description should at minimum note permissions, uniqueness constraints, and what the created resource looks like. As written, an agent cannot tell whether the call is idempotent, what it returns, or how the result plugs into add_contacts.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100% – the schema already documents name length limits, the description field, and the double_opt_in default. The description adds no additional meaning beyond the schema, so baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb ('Create') and resource ('contact list') plus a brief purpose ('organizing recipients'), so an agent knows exactly what it produces. It does not, however, distinguish this from sibling list operations such as create vs. list_contact_lists / update_contact_list, leaving differentiation to the name alone.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
There is no guidance on when to use this versus the other contact-list tools, no preconditions (e.g., whether a list name must be unique across the account), and no mention of follow-up steps like add_contacts. Usage must be inferred entirely from the tool name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.