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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the mutation nature is known. The description adds the partial-update behavior (unchanged fields remain untouched), which is real added value. No contradiction with annotations, but no further disclosure about validation, no-op calls, or response behavior is provided.

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?

A single efficient sentence that front-loads the purpose before the usage instruction. No wasted words; appropriately minimal for a tool whose parameters are fully documented in the 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?

For a simple tool with three optional parameters, full schema coverage, and an output schema, the description is adequate. It covers partial-update semantics but omits the self-vs-other-user distinction relative to update_user and any validation notes — minor gaps given the simplicity.

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 100%, so the schema already documents all three parameters (theme, fullname, language) with enums for two. The description adds nothing beyond the schema; the baseline 3 applies since the schema carries the full documentation burden.

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 states a clear verb-resource pair ('Update the authenticated user's profile'), which distinguishes this from sibling update_user by restricting scope to the authenticated user's own profile. It's specific and identifiable, though it doesn't name the sibling it differs from 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?

'Only include the fields you want to change' gives genuine partial-update (PATCH) semantics, which is useful for an all-optional-parameter tool. However, it never references the natural alternative update_user or get_current_user, so an agent must infer when self-update is the right choice vs. updating another user.

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