measurements_update_head_circumference

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

No annotations are provided, so the description carries the behavioral burden. It usefully discloses partial-update behavior with 'Only provided fields are changed' and the existing-record precondition, but it does not mention what happens when the ID is not found, authorization needs, or other side effects.

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 two short sentences with no filler. The purpose is stated first, followed immediately by the most important behavioral qualifier, making it easy for an agent to parse quickly.

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 CRUD update with a fully described input schema and an output schema, the description plus schema is sufficient for correct invocation. It lacks error-handling and alternative-tool guidance, but those are not necessary to invoke the tool correctly in the common case.

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%, so the baseline is 3. 'Only provided fields are changed' adds meaningful patch semantics beyond the schema's individual parameter descriptions by clarifying that omitted fields are not overwritten. It still leaves explicit null-vs-omitted behavior unspecified, so it does not fully reach 5.

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 identifies a specific verb and resource: 'Update an existing head circumference record.' This distinguishes it from the create/delete/list siblings by resource and by the 'existing' qualifier, though it does not explicitly name an alternative tool.

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?

'Existing' implies this tool is for updating records that already exist, not for creating new ones, which gives some usage context. However, it does not explicitly say when to use this tool versus create_head_circumference or delete_head_circumference, and no alternatives are named.

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