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

Annotations already indicate this is a write operation (readOnlyHint=false) and not destructive (destructiveHint=false). The description adds the behavioral detail that only provided fields are changed, which is useful. However, it does not mention any side effects, permissions, or what happens to omitted fields (beyond implying they are unchanged). Given the annotations cover the safety profile, a 3 is appropriate.

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?

The description is a single, clear sentence that front-loads the purpose and includes the key usage hint. Every word earns its place with no redundancy.

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 simple partial-update tool with an output schema present (so return format is not required), the description covers the essential behavior and scope. It could explicitly mention that the update applies only to the authenticated user (already implied) or differentiate from 'update_user', but the current description is largely sufficient. A 4 is appropriate.

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?

The input schema has 100% coverage with descriptions for all three parameters (theme, fullname, language). The description adds no additional parameter-specific meaning beyond the schema, so the baseline of 3 is correct.

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?

The description clearly states the verb ('Update') and the resource ('the authenticated user's profile'), which distinguishes it from generic 'update_user' by specifying the scope (self). However, it does not explicitly differentiate from siblings like 'update_my_avatar' or 'update_notification_preferences', so it falls short of a 5.

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 provides a useful guideline: 'only include the fields you want to change', which clarifies partial updates. But it does not explicitly state when to use this tool versus alternatives such as 'update_user' (for other users) or 'update_my_avatar' (for avatar only). The context is implied rather than explicit.

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