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

Annotations only supply destructiveHint=true, so the description carries real weight here and delivers the most important behavioral fact: list-valued fields (emails, phones, groups, companies) REPLACE existing values rather than merging, while omitted fields are left untouched. That replacement warning is exactly what an agent needs before calling a destructive PATCH, though auth requirements and failure behavior are still unstated.

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?

Three tight sentences, front-loaded with the mutation and its replacement caveat, ending with the API endpoint. Nothing redundant and nothing missing that belongs here.

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 15-parameter mutation tool with no output schema and only destructiveHint in annotations, the description covers the critical partial-update and replacement semantics that could otherwise silently destroy data. Missing only secondary details such as permissions, error responses, and whether the update is atomic.

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, but the description adds value the per-field schema text does not: the aggregate rule that only supplied fields mutate and that all list-valued parameters are wholesale replacements. It still adds no format or validation detail beyond the schema, so it does not reach a 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?

States a specific verb and resource ('Update fields on an existing person') and even pins the underlying REST operation (PATCH /v1/people/{id}), which clearly separates it from folk_create_person and folk_get_person. It stops short of naming those siblings explicitly, so an agent still infers the routing rather than reading it.

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 'Only provided fields are changed' clause implies a partial-update use case, but there is no explicit when-to-use / when-not-to-use guidance and no named alternative (e.g. use create for new people). Usage is implied rather than stated.

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