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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the safety profile is covered externally. The description adds one genuinely useful behavioral fact — the write goes directly to the control rather than through synthetic keystrokes, so keyboard-shortcut side effects won't fire. It says nothing about failure modes, focus requirements, or what happens when the control rejects a value.

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 the primary action front-loaded and the disambiguation clause second. No filler, nothing buried.

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?

Output schema exists, so return values need no explanation, and annotations carry the safety profile. But for a destructive, non-idempotent tool with 18 params and multiple targeting backends (DOM/CDP, OCR, coordinates), the description omits the fallback logic and any verification guidance beyond 'validate the target' — meaningful gaps for a tool this broad.

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 every one of the 18 parameters is already documented in the schema; baseline 3 applies. The description adds only indirect color ('identified native accessibility control'), giving no guidance on choosing among id/label/name/role targeting or the target enum values.

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 (assign a value to a native accessibility control) and names the canonical case (editable text field). The clause 'this changes the control rather than sending a keyboard shortcut' effectively separates it from computer_type/keyboard, though it never names the closest siblings (ui_set_value, computer_select, computer_set_range_value) directly.

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?

'Validate the target before writing' gives a precondition, and the shortcut contrast implies 'use this instead of typing' for accessibility controls. But it never says when to prefer browser_set_value or computer_select/computer_set_range_value, leaving the 18-param targeting decision (auto/ui/ocr/coordinates) unexplained.

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