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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds useful disclosure about the response payload and the conditional transcript ('when one is stored'), but says nothing about ordering, pagination, or truncation behavior.

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?

A single front-loaded sentence that states scope first, then the payload. Every clause carries information and nothing is padded.

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 does carry the minimum return-value information (caller, time, duration, transcript). However, it omits ordering, pagination/limit behavior, and how to retrieve the full transcript or a single voicemail, which are material for a listing tool with a get_voicemail sibling.

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 both optional parameters (days, limit) are documented in the schema itself with defaults and bounds. The description adds no syntax or format detail beyond what the schema already provides, 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?

The description names a specific verb (Returns) and resource (voicemails) plus the scope 'on this seat', and it enumerates the returned fields (caller, time, duration, transcript). It does not, however, distinguish itself from the sibling get_voicemail, so an agent must infer that this is the bulk/recent listing.

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, no mention of the get_voicemail alternative for a single item, and no exclusion criteria. 'Recent' is the only usage signal and it is undefined in the description (the 30-day default lives only in the schema).

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