updateUserPhoto

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

Discloses partial update behavior, live data writing, and the special _clear_fields mechanism. Adds context beyond annotations (which are not contradictory). Returns the updated record.

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?

Concise and well-structured: one-line summary, then bullet points for usage, required fields, enums, see also, and return format. Every sentence adds value.

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?

Comprehensive for a 3-parameter tool: covers the main update functionality, the special _clear_fields parameter, links to related tools, and documents the return format (since no output schema).

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?

Adds meaning for `type` (lists enums and use case) and `_clear_fields` (explains how to clear fields, availability across updates, and distinguishes from setting empty string). This compensates for the low schema coverage (33%).

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?

Clearly states the verb 'Update', resource 'user photo', and behavior 'update by ID, fields omitted untouched, writes live data'. Also distinguishes from siblings by referencing createUserPhoto and deleteUserPhoto.

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?

Explicitly says 'Use when: changing a photo's type slot' and provides required parameter. Mentions alternatives via 'See also' and includes a detailed note on clearing fields via _clear_fields.

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