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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and non-open-world, so the safety profile is covered. The description adds nothing beyond that: it does not mention pagination via cursor, result limits, or what the list contains. With the annotation bar already met, the description's contribution is essentially zero.

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?

Three words and one sentence: efficient in the sense of having no waste, but this is under-specification rather than conciseness. There is nothing to front-load because nothing was provided.

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?

With no output schema, the description is the only place to explain the return shape and the cursor-based pagination contract, and it says none of that. For a list tool with an undocumented paging parameter, an agent cannot tell how to page through results or how to interpret an external_id miss.

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 only 33% — only external_id is documented in the schema, while limit (default 25, max 100) and cursor have no descriptions anywhere. The description does not compensate for this gap; it never mentions limits, paging, or the external_id lookup mode.

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?

"List your customers" essentially restates the tool name and title, adding no scope information (what a customer is versus a contact, whether it is paginated, whether filters exist). It is not misleading, but an agent learns nothing it did not already get from the name.

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 when-to-use guidance at all, despite many plausible alternatives in the sibling set (get_customer, list_contacts, query_audience, list_lists). No prerequisites, no exclusions, and no routing hint are given.

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