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

No annotations are provided, so the description must disclose behavioral traits. It mentions the automatic 250ms delay and the validation of reportLen, which is helpful, but it does not disclose mutation semantics (creation is a write operation), error behavior, return values, or any prerequisites. This is insufficient for a tool with no annotation safety profile.

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 with zero fluff. The purpose is front-loaded, key parameters are explained inline, and the important behavioral note (250ms delay) is included. Every word 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?

The description covers the core purpose and a key timing detail, but it lacks lifecycle context (e.g., that the device must be destroyed later), prerequisites (e.g., device must be connected), or error conditions. For a creation tool with no output schema, this is a moderate gap that could mislead an agent about the full operation.

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 adds clarity by explaining descriptor is base64-encoded HID report descriptor bytes and reportLen is the exact byte-length for validation, which enriches the schema's terse descriptions. It adds meaningful semantic value 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 action (Register) and a clear resource (virtual HID device on an Android device) with the mechanism (device control channel). It is unambiguous about what the tool does, even without explicit sibling differentiation, and the mention of descriptor/reportLen ties directly to its purpose.

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 implies the tool is used before sending INPUT via the 250ms delay note, but it does not explicitly state when to use this tool versus alternatives (e.g., device_uhid_input, device_uhid_destroy). No exclusions or explicit conditions are provided, leaving the agent to infer the context.

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