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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety burden is covered. The description adds real behavioral value by defining the three result categories (added / re-studied as a new edition / removed) and the empty-input shortcut, though it says nothing about result size or what happens to malformed or unknown IDs.

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 sentences, front-loaded with the comparison operation and followed by the one edge-case rule an agent needs. Nothing is redundant with the title or 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?

The tool has one fully documented parameter, an output schema, and rich annotations; the description fills the remaining conceptual gap — what the diff categories mean and how to request a full listing. An agent can call this correctly without further information.

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 schema already explains the slug@sha256 digest form, so the baseline is 3. The description goes beyond it by giving the empty-list semantics, which the schema does not state and which is the key non-obvious usage of the parameter.

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: it compares the caller's cached voice IDs against the current release and reports added, re-studied, and removed voices. This is clearly distinct from the fetch-one (get_voice), packet (get_voice_packet), and lookup (search_voices) siblings, which do not describe a diff operation.

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 makes the use case clear — syncing a local cache with the current release — and states the bootstrap case (empty list returns everything as added). It does not explicitly name siblings or say when not to use it (e.g., fetching a single voice by ID), so a small routing gap remains.

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