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

Adds real behavioral detail beyond the annotations: non-destructive to the source, and a failing target is refused with the list of mailboxes that were seen. However, annotations declare destructiveHint=true and the description never explains why — e.g. what happens if the message already exists in the target mailbox, whether it is overwritten or duplicated. That is the key risk an agent needs before calling a destructive-flagged tool.

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 sentences, front-loaded with what the tool does before the conditional cross-account rule and the failure behavior. Slightly dense parenthetical ('with account= the target is looked for in that account only') but every clause carries information.

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?

An output schema exists, so return values need not be explained, and the description covers the tricky bits: cross-account targeting and error reporting on a missing folder. Missing is any statement about collision/overwrite behavior in the target mailbox, which matters given destructiveHint=true.

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; the description earns above that by explaining the cross-account semantics of 'account' (omit it to target another account's mailbox; supply it to scope the lookup to that account), which the schema only says as 'pass it so the message is found in the right account'. It does not clarify the interaction between the required 'target_mailbox' and the optional 'mailbox'.

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 ('Copies an email'), the exact resource and destination ('another mailbox of the Mac's Apple Mail'), and clarifies the source is untouched ('the original stays where it is'), which implicitly separates it from move_email. It never names the sibling it is contrasted with, so the differentiation is inferred rather than explicit.

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?

Gives a concrete when-to-do-what rule for the cross-account case: leave 'account' out and use a folder name unique to the target account, versus supplying 'account' to scope the search to that account. No guidance on when to prefer move_email or send_email instead, and no prerequisites (permissions, Mail.app state) are mentioned.

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