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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=true, so the mutation/idempotency profile is covered. The description adds value beyond that with auth context ('uses the connected Himalayas account; no extra sign-in needed'), though it does not explain why a timezone change carries a destructive hint.

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 sentences, all front-loaded and each carrying distinct information: purpose, sibling routing, and auth scope. 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 one-parameter mutation with no output schema and full annotation coverage, the description supplies everything needed: what changes, what it affects, where to go for related edits, and that no re-authentication is required.

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?

There is a single parameter with 100% schema description coverage, including format examples like 'Pacific Time (US & Canada)' and 'London'. The description adds nothing about the time_zone value beyond the schema, 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?

States a specific verb and resource ('Change the user's account time zone') and adds the effect ('used for email timing'), which distinguishes it from the many other update_* siblings. It explicitly names update_profile as the place for name changes, so an agent can route without opening schemas.

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?

Gives explicit when-not guidance: name belongs on update_profile, and email address and password can only be changed on himalayas.app. This routes the agent away from the wrong tool rather than leaving it to infer.

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