list_contacts

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

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It mentions the GET endpoint and domain-first model, but does not disclose pagination behavior, response format, rate limits, or any side effects. For a list operation with after/before/limit parameters, this is a significant gap.

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?

The description is a single sentence that front-loads the core purpose and endpoint, with the segment restriction added as a secondary note. There is no wasted verbiage, though it could be more informative within the same length.

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 list tool with five parameters and no output schema or annotations, the description is too terse. It lacks explanation of pagination (after/before/limit), response structure, or any filtering beyond segment_id. The domain-first note is helpful but not sufficient for an agent to call it correctly without guessing.

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 40% (only domain and segment_id have descriptions). The description only repeats the segment_id restriction and does not add any meaning for after, before, or limit. It fails to compensate for the undocumented parameters, leaving agents without guidance on how to paginate or control results.

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?

The description clearly states the tool lists contacts for a sending domain, with a specific verb ('List') and resource ('contacts'). It also gives the endpoint and mentions the optional segment restriction. It doesn't explicitly differentiate from sibling list_segment_contacts, but the domain-first focus makes the purpose unambiguous.

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 implies usage: it can list all contacts for a domain, and with segment_id it restricts to a segment's members. However, it never explicitly tells the agent when to use this tool versus alternatives like list_segment_contacts or list_contact_segments. No exclusions or alternative names are provided, so guidance is only implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.