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

Annotations already declare readOnlyHint and openWorldHint, and the description adds genuinely new behavior: the API returns the entire list while this tool truncates to `limit` and reports the total, which is important for an agent reasoning about completeness. It does not state ordering or whether the total reflects pre- or post-pagination counts, but the truncation disclosure is the key trait.

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 tight sentences, front-loaded with the resource and its significance, then pagination behavior, then the underlying REST call. Every clause carries information and nothing is repeated from the schema.

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 still tells the agent what each row contains (number, date added, reason) and warns that results are truncated with a total provided. Combined with annotations, that is enough to call this correctly without exploring further.

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 100%, so `limit` and `offset` are already documented with defaults and bounds. The description reinforces the semantics of `limit` ('shows the first `limit` entries') but says nothing about `offset` beyond the schema, 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 specific verb and resource — list phone numbers in the account's optout database — and even names the fields returned (number, date added, reason). It never contrasts itself with the closest sibling (smseveryone_get_contact_list / smseveryone_list_contact_lists), so an agent must infer that this is the suppression list rather than the marketing contact list.

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?

Usage is implied rather than stated: the parenthetical 'messages to them are never sent' tells the agent why the list matters, and the paging note implies use when enumerating opt-outs. There is no explicit when-to-use, when-not-to-use, or pointer to smseveryone_add_optouts as the write counterpart.

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