List phone numbers

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

Annotations already declare readOnlyHint and openWorldHint, so 'Read-only' adds nothing. The description does add real behavioral context the annotations lack: pagination is stateless, page/per_page (or limit/offset) must be passed on every call, and nothing persists between calls. That is the kind of call-pattern disclosure that prevents an agent from assuming server-side cursor state.

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?

Four sentences, front-loaded with what is listed and immediately followed by filtering and pagination constraints. The only waste is the trailing 'Read-only,' which merely restates the readOnlyHint annotation.

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 usefully enumerates the returned fields and covers the stateless-pagination contract, so an agent can call it correctly. The remaining gap is the undefined 'page' parameter and status enum semantics, which are left entirely to the schema.

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 50%: search and per_page are documented in the schema, while page and status are not. The description partially compensates by naming the status filter and the pagination pair, and even reveals an undocumented limit/offset alternative. However, it gives no semantics for 'page' or for the status enum values, so it lands at the baseline-plus level rather than fully compensating.

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?

Specific verb ('List') plus resource ('phone numbers on this Vobiz account and its sub-accounts') plus the returned fields (status, capabilities, linked application, fees). This cleanly separates it from the sibling list_messaging_numbers, which targets a different number type, so an agent can route without opening schemas.

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?

It notes the supported filters ('Supports status filter and search'), which implies how to narrow results, but never says when to use this list versus get_phone_number_details, get_number_health, or search_available_numbers. No exclusions or prerequisites are stated, so usage is only implied.

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