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

Annotations already declare idempotentHint=true, destructiveHint=false and readOnlyHint=false. The description adds genuine value beyond them: the explicit failure mode ('Returns "no HID available" on iOS 17.x / no-tunnel') and the no-session/no-foregrounding traits, which an agent could not learn from the annotations.

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 tight sentences with zero filler; the core action is front-loaded and the error condition follows immediately. Every clause 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 two-param idempotent write with no output schema, the annotations cover the safety profile and the description supplies the environment failure mode. Only the sibling disambiguation (set_pasteboard vs this HID variant) 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% (both udid and text documented inline), so the schema carries the parameter burden. The description adds no syntax, format, or constraint detail for either parameter; baseline 3 applies.

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+resource ('Write the device clipboard (pasteboard)') plus the mechanism ('via the system clipboard service'). It does not name the obvious sibling alternative (ios_set_pasteboard), so an agent must infer the distinction from the mechanism phrase rather than a direct contrast.

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?

'no automation session needed, no app foregrounding' implies the usage context (call this when you lack a session) but the description never explicitly states when to prefer this over ios_set_pasteboard or ios_clipboard_get_hid. Usage is inferable rather than stated.

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