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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the description only needs to add context beyond that. It does so by specifying the return dictionary with similarity, match, and threshold keys, giving the agent a concrete expectation of output without contradiction.

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?

The description is extremely compact: one clarifying question defines the operation, followed by a short return specification. Every sentence earns its place and there is no 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 simple read-only verification tool, the description is nearly complete: it states the core behavior, the enrolled-speaker context, and the return shape despite there being no output schema. A small gap remains around how speaker_id maps to the enrolled speaker and how match relates to threshold, but the tool is still invocable with reasonable confidence.

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 reported as 100%, so the baseline is 3 even though the description adds no input-parameter semantics beyond the output threshold key. The description does not clarify speaker_id, and notably speaker_id appears as required but has no property entry in the schema, yet the description also does not compensate for this gap.

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 states a specific operation: 1:1 verification of a clip against an enrolled speaker. The phrase 'is this clip the enrolled speaker?' makes the resource and action unambiguous, and '1:1' differentiates it from the sibling voice_id_identify, which is presumably 1:N identification.

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?

The description clearly frames this as the 1:1 use case, which gives an agent a clear reason to select it over voice_id_identify or voice_id_enroll. It does not explicitly name alternatives or state when not to use it, but the 1:1 framing provides adequate context.

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