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

Annotations already declare destructiveHint=true, readOnlyHint=false and non-idempotent, so the safety profile is covered. The description adds genuine behavioral value beyond them: the same-filesystem constraint, the concrete failure mode, and the copy-then-delete workaround. It stops short of stating overwrite behavior when the destination exists or root/permission requirements.

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?

Two sentences, front-loaded with the action, followed by the constraint and fallback. No filler; every clause carries information the agent needs.

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 three-parameter destructive mutation with no output schema, the description covers the main operational pitfall (cross-filesystem failure) and the rename capability. It could go further on destination-overwrite semantics and permission prerequisites, but nothing essential for correct invocation is missing.

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% with three well-documented parameters, so the baseline is 3. The description adds only marginal meaning to the 'to' parameter by implying it can be a new name (rename) as well as a destination path, but it gives no syntax or path-format detail beyond the schema.

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 ('Move or rename a file or directory on the device') and immediately distinguishes itself from the platform sibling by naming ios_file_move as its counterpart. An agent can pick this tool correctly without opening the 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 gives the when-not condition (both paths must be on the SAME filesystem; /sdcard to /data fails) and the alternative workflow (copy then delete). This is exactly the routing guidance an agent needs versus device_file_copy.

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