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

Annotations already declare destructiveHint=true and idempotentHint=false, but the description adds valuable context beyond them: the copy is device-side so bytes never travel to the server, directories are refused because there is no recursive copy, and failing is preferred over false success. That rationale for the error path is exactly the kind of behavioral disclosure annotations cannot provide.

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 sentences, each earning its place: operation and scope first, routing advice second, directory-raison d'être third. It is front-loaded and contains no filler.

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 moderate-complexity file copy with a fully described schema and rich annotations, the description supplies the remaining decision-relevant context: same-root preference, directory restriction, and the alternative workflow. It does not need to explain return values because no output schema exists and the operation reports straightforward success/failure.

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 the baseline is 3. The description reinforces the same-root constraint that the schema already gives for "to", but adds no extra meaning for udid, bundleId, or remotePath beyond what the schema documents.

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 ("Duplicate") and resource ("ONE file") with scope ("to another path on an iOS device"), which cleanly distinguishes it from ios_file_move, ios_file_pull, and ios_file_push. An agent can tell it is a same-root, single-file copy without opening any schema.

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 routes the agent: prefer this over pull-then-push when both paths are in the same root, and it names the exclusion (directories are refused). It also gives the corrective workflow (walk the tree with ios_file_list and copy the files), so when-to-use and when-not-to-use are both covered.

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