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

Annotations already declare readOnlyHint=false and destructiveHint=false, but the description adds real behavioral value with 'Only the fields given change', i.e. merge/patch semantics that an agent must know to avoid clobbering untouched fields. It does not mention side effects such as email verification flows or avatar URL validation, which keeps it from a 5.

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 verb and resource, then the field list, then the partial-update rule. No filler, nothing that doesn't earn its place.

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 9-parameter all-optional mutation with no output schema and thin schema descriptions, the definition covers every parameter by name plus the merge semantics, which is close to sufficient. It stops short of noting whether email changes trigger verification or what the response returns, minor gaps for an otherwise complete definition.

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 only 33% (only locale, timeZone, and defaultScheduleId are documented), so the description carries meaningful weight by mapping human terms to parameter names: 'language' to locale, 'avatar' to avatarUrl, 'default schedule' to defaultScheduleId. It doesn't add format or constraint details beyond what the schema already encodes.

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 (change) and resource (the user's profile) and enumerates the affordances: name, email, bio, time zone, week start, time format, language, avatar, default schedule. It is clearly distinguishable from adjacent tools like update_notification_prefs or update_schedule, though 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?

The closing clause 'Only the fields given change' communicates partial-update semantics, which tells the agent it may send any subset. There is no explicit guidance on when to prefer this over update_notification_prefs or update_schedule, nor any prerequisite or exclusion note.

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