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

The annotations already flag destructiveHint=true, and the description adds genuinely useful semantics beyond that with the partial-update guarantee and the underlying endpoint. However, it never reconciles that with the destructive hint or warns which fields behave destructively — the schema silently says tags, emails and phone_numbers are 'Replace'-style wholesale overwrites, which the description does not surface.

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 short, front-loaded sentences: what it does, the partial-update contract, then the API mapping. No filler and nothing important buried.

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 9-parameter mutation with no output schema, the description plus full schema coverage covers the essentials. Minor gaps remain: no note on the destructive array-replacement behavior, permission requirements, or what a successful response contains.

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 every parameter is already documented in the input schema and the baseline is 3. The description adds the cross-cutting rule that unchanged fields are preserved, but no per-parameter meaning beyond what the schema states.

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 gives a specific verb and resource ('Update fields on an existing person') and pins the scope of the change with 'Only provided fields are changed'. The word 'existing' implicitly separates it from copper_create_person, but no sibling tool is named or explicitly contrasted, so it stops short of the top band.

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?

Usage is implied rather than stated: an agent can infer this is the call for modifying a person that already exists rather than creating one. There is no explicit when-to-use/when-not guidance, no mention of prerequisites (e.g. valid person id, permissions), and no routing to alternatives such as copper_create_person or copper_get_person.

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