add-contacts-to-listAdd contacts to a list while preserving their existing memberships. May trigger automations that send messages.
Add contacts to a list, keeping their other memberships. This can start the organization's active automations, which may send messages.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | The list id. | |
| contact_ids | Yes | Contact ids, from list-contacts. |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only give the generic flag set (non-read-only, non-idempotent, non-destructive), which understates real impact. The description adds the crucial behavioral fact that adding contacts can fire the organization's active automations and send messages — a non-reversible external side effect an agent must know before calling.
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?
Two tight sentences: the operation and its additive nature come first, the side-effect warning second. Every clause carries information and nothing is padded.
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 two-parameter mutation with no output schema, the description covers the key risk (automation-triggered messages) and the additive semantics. It omits whether the call returns counts or errors on invalid contact ids, but with no output schema that omission is minor.
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%, so both parameters (the list uuid and the contact_ids array with minItems 1 and provenance 'from list-contacts') are already documented. The description adds no format, batching, or limit detail beyond that, so the 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 concrete verb+resource ('Add contacts to a list') and clarifies the additive semantics with 'keeping their other memberships', which implicitly distinguishes it from remove-contacts-from-list and from any replace-style operation. It does not name a sibling explicitly, so it falls just short of the top tier.
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?
No when-to-use guidance, no prerequisites, and no named alternative. The sentence about starting automations describes a consequence of invoking the tool rather than a condition for choosing it over remove-contacts-from-list or a tag-based approach.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.