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

Annotations already declare the mutation profile (readOnly=false, destructive=false, idempotent=false), so the description's job is to add context, which it does: it discloses the auto-applied ~250ms post-CREATE settling delay and the validation role of reportLen. It stops short of stating failure/conflict behavior (e.g., duplicate id handling).

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 tight sentences, each earning its place: identity/action first, then the two non-obvious parameters, then the timing behavior. Front-loaded and free of 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?

With no output schema, the description covers the essential creation semantics plus the timing behavior an agent needs. It omits what happens on id collisions or whether an existing device must be destroyed first, which would fully close the loop for a non-idempotent mutation.

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, but the description adds real meaning beyond the schema strings: it clarifies that descriptor is the base64 report descriptor bytes and that reportLen is the exact per-report INPUT length used for validation. This contextualizes why those two fields matter rather than merely restating them.

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 states a specific verb and resource ('Register a virtual HID device on an Android device via the device control channel'), and the lifecycle language ('After CREATE ... accepts INPUT') makes clear it is the setup step of the UHID family. It does not name sibling tools like device_uhid_input or device_uhid_destroy directly, so sibling differentiation is implied 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?

Usage is implied through the CREATE-then-INPUT lifecycle referenced in the delay sentence, which tells the agent this precedes input injection. However, there is no explicit 'when to use this vs. alternatives' or a named downstream tool ('use device_uhid_input after this'), so guidance remains inferred rather than stated.

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