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

Annotations already declare readOnlyHint=true, and the description adds meaningful behavior beyond them: the URL is temporary with a 3-hour validity window, it can be used to stream or download, and it maps to a specific API endpoint. Auth requirements and rate limits are not mentioned, keeping it from a 5.

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?

Two tight sentences with the core capability and the key constraint (3-hour expiry) front-loaded. Zero filler.

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?

For a single-parameter read tool this is nearly complete: the id source, the purpose, the expiry, and the endpoint are all covered. A minor gap is that the return shape (field name for the URL, whether an expiry timestamp is included) isn't described, though no output schema exists to cover it.

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% and the single parameter is already documented as 'The voicemail id (`voicemail.id`)'. The description repeats and slightly extends this by noting the id comes from a call or voicemail record, but adds little beyond the schema — baseline 3.

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 ('Get a temporary URL ... to stream or download a voicemail') plus scope details (3-hour validity, id source, endpoint). It doesn't explicitly differentiate itself from the near-sibling rinkel_get_call_recording_url, so it falls just short of a 5.

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 by 'stream or download a voicemail' and the id source is clarified, but there is no explicit statement of when to prefer this over rinkel_list_voicemails or rinkel_get_call_recording_url, and no when-not guidance.

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