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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false; the description adds the blast radius ('affecting every reminder without an override'), which is exactly the kind of impact context annotations can't express. It stops short of saying whether omitted optional fields retain current values or clear them.

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?

Three short routing/context sentences followed by a tight parameter block; the scope warning is front-loaded and no sentence is redundant given the bare 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?

Output schema exists, so return values need no explanation, and alternatives plus every parameter are covered. The one gap is the all-optional, null-defaulted schema: the description never says what happens to a field the caller omits.

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 0% and contains no enums, so the description carries the full burden and does: voice_id provenance, the four literal personality values, BCP-47 language examples, the meaningful speaking_rate range with a use-case rationale, and the meaning of greet_by_name. This is materially more than the schema provides.

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 ('Change the account's DEFAULT voice') and immediately scopes the effect ('affecting every reminder without an override'), which cleanly separates it from set_reminder_voice. An agent can pick it without opening the schema.

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?

Explicitly routes to the alternative for the narrow case ('For a single reminder only, use set_reminder_voice instead') and names the lookup/preview tools (list_voices, preview_voice) with their purpose. Both when-to-use and when-not-to-use are stated.

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