Add contacts by ID to a mailing list, returning the count of newly added contacts while ignoring duplicates. Requires a management session token.
Add contacts (by id, ctr_…) to a list. Returns how many were newly added; contacts already on the list are ignored. Requires a management session token.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Path parameter `id`. | |
| contactIds | Yes |
Changes observed during successful MCP inspections.
v0.20.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds useful behavioral detail beyond annotations: contacts already on the list are ignored, and the return value is the count of newly added contacts. It also discloses the auth requirement. No contradiction with annotations.
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 concise sentences that front-load the action, return behavior, and auth requirement. No filler or redundant repetition of schema fields.
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 annotations and no output schema, the description covers the core essentials: return value, duplicate handling, and auth. The main gap is explicit parameter-to-field mapping, but the tool name and ID pattern make this mostly inferable.
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 coverage is only 50% with minimal property descriptions ('Path parameter id' and an untyped string array). The description partially compensates by mentioning 'ctr_' contact IDs, but it does not explicitly map 'id' to the list ID or explain the format/limitations of contactIds.
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?
Description uses a specific verb ('Add'), names the resource ('contacts') and target ('a list'), and clarifies contacts are identified by IDs with a 'ctr_' prefix. This clearly distinguishes the operation from sibling list/remove tools.
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?
The description provides context by noting the management session token requirement and implies the use case of adding contacts to a list. However, it does not explicitly discuss when not to use this tool or mention alternative siblings for removing/listing contacts.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.