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

With no annotations, the description carries the full behavioral disclosure burden. It adds valuable traits: the copy is device-side (bytes never travel to the server), and directories are refused with the rationale that reporting success after copying nothing would be worse than an error. This explains expected error behavior and architectural efficiency, though it omits overwrite semantics and mutation warnings.

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 with zero waste: the purpose is front-loaded, the device-side fact is brief but informative, and directory handling is explained with actionable guidance. Every sentence earns its place.

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 4-parameter tool with no output schema and no annotations, the description covers the operation, when to use it, performance characteristics, and error behavior for directories. It doesn't mention overwrite behavior or return values, but the schema already documents parameters, and the description gives sufficient guidance to call the tool correctly.

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 baseline is 3. The description reinforces that remotePath must be a file (not directory) and that both paths must be in the same root, which partially overlaps with the schema ('within the same root'). It doesn't add new syntax or format details beyond the schema, so the baseline 3 is appropriate.

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 opens with 'Duplicate ONE file to another path on an iOS device,' a specific verb+resource+device scope that clearly distinguishes it from move, pull, push, and delete siblings. It also explicitly states directories are refused, further narrowing the boundary.

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 description gives an explicit conditional preference: 'prefer this over pull-then-push when both paths are in the same root,' and for directories it directs to 'walk the tree with ios_file_list and copy the files.' This names alternatives and the conditions that select them, leaving little to inference.

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