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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still adds meaningful domain context — that a list only takes effect once attached to a SIP/PSTN trunk, and that entries are omitted in favor of items_count. This is valuable behavioral insight beyond the 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?

Front-loaded with the core purpose and the definition of a Voice IN Number List before moving to return details. It is dense and runs long, but each sentence carries functional information and little is redundant.

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 must carry the return contract, and it does so thoroughly: id, name, mode, default_action, items_count, attached_trunks (up to 10), creation time, and pagination meta. Nothing needed to call or interpret the tool is missing.

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 100% and all three parameters (name, page, page_size) are documented in the schema. The description restates the case-insensitive partial name match and pagination but adds no syntax or format detail 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 the authenticated customer's Voice IN Number Lists') and immediately defines what a list is: caller-ID (source number) filters for inbound calls. It clearly distinguishes itself from the sibling get_voice_in_number_list by noting that list entries are not returned here.

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?

Explains that results are optionally searched by name and paginated, and explicitly routes the agent to get_voice_in_number_list for the entries themselves. It lacks an explicit 'do not use this when...' exclusion, but the alternative-tool routing is clear.

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