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

Annotations already establish readOnly/idempotent/non-destructive, so the description is free to add return-shape context: the exact response fields (name, mode, default_action, items_count, attached_trunks_count with up to 10 named trunks, pagination meta) and the constraint that entries are never returned wholesale. That is meaningful added behavior beyond the safety hints, though it does not discuss permissions or failure modes.

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 action, then the return contents, then pagination guidance. Three dense sentences with no filler, though the enumeration of response fields is slightly long for a description that could lean on a 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 compensates by enumerating the returned fields, the exact-value guarantee, the allow/reject action, and the pagination model. An agent has everything needed to call this tool and interpret the response.

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 all three parameters (id, page, page_size) are already documented with defaults and bounds. The description reinforces their purpose ('page/page_size to walk large lists') and notes where the id comes from, but adds no syntax or format detail beyond the schema, so the baseline 3 is correct.

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 (Show) and resource (one Voice IN Number List including its stored entries) with scope ('one of the authenticated customer's'), plus a parenthetical that explains what a Voice IN Number List is. This cleanly distinguishes it from the sibling list_voice_in_number_lists, which enumerates lists rather than returning one list's contents.

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 names a concrete downstream use case (entries are needed character-for-character by update_voice_in_number_list remove_numbers) and gives pagination guidance ('Use page/page_size to walk large lists — entries are never returned wholesale'). It does not explicitly contrast with the sibling list tool or state when not to use it, so it falls short of a full 5.

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