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

Annotations already cover safety and idempotency, so the description's real contribution is the side-effect boundary: 'It does not change anything already delivered' — i.e. past messages keep the old name. It also states the 80-character cap, a constraint absent from annotations and schema. No detail on the response, but with no output schema that is the sole remaining gap.

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?

Four short sentences, front-loaded with purpose and followed by trigger, constraint, and side-effect caveat — no filler. Slightly dense run-on in the first sentence, but each clause carries distinct information.

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 account mutation with annotations covering safety/idempotency and no output schema, the description supplies purpose, trigger, length limit, source-of-value guidance, and the non-retroactive behavior. Nothing an agent needs to call this correctly is missing.

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 param is well described, so the baseline would be 3. The description earns above baseline by adding two rules not in the schema: the 80-character maximum and 'Use the user's own words for their name', which steers the agent away from generating or reformatting a name.

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?

Specific verb + resource: 'Set the name this account goes out under', with scope clarified as the account-level display name shown on every package, contact request, and notification. That scope phrasing implicitly separates it from contact-renaming siblings like rename_contact, but no sibling is named explicitly.

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 an explicit trigger condition tied to a named sibling: 'Offer it when whoami reports the name as a placeholder made from the address.' The rationale (what a stranger sees on a first message) tells the agent both when and why to invoke it.

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