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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false. The description adds genuine context beyond those flags: the cursor is moved to the end, exactly N backspaces are sent based on the current text length, and the field must already be focused. It stops short of noting edge cases such as an empty field or non-text focused elements, so it is helpful but not exhaustive.

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 compact sentences, action and mechanism front-loaded, followed by the prerequisite and the alternative. No filler; every clause carries information.

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 destructive, non-readOnly mutation with no output schema, the description covers mechanism, prerequisite, and the preferred alternative path. It omits only minor edge behavior (e.g., clearing an already-empty field, non-text targets), which keeps it just short of fully complete.

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?

There is a single parameter (udid) with 100% schema description coverage, so the schema carries the meaning and the description adds nothing about parameters. This matches the baseline 3 for high-coverage schemas.

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 names a specific verb and resource ('Clear the focused text field on Android') and even explains the mechanism (reads text length, sends that many DELETE keycodes). It is impossible to confuse with device_type, which is named and distinguished explicitly.

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?

It states the precondition ('Tap the field to focus it first') and routes to the alternative for the related case ('To clear and re-type in one call, use device_type with clearFirst:true instead'). Both the when and the when-not are explicit.

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