Set field value

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

Annotations already declare destructiveHint=true and idempotentHint=true. The description adds valuable behavioral context: it operates through the accessibility API without keystrokes, discards the previous value, and reports rejection via the result. No contradiction with 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?

Three sentences, each earning its place: the first states purpose, the second gives usage guidance, the third adds behavioral detail. Front-loaded with the core action, no filler or redundancy.

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 simple 2-parameter mutation tool with annotations covering safety, the description covers the key runtime scenario (fallback on rejection) and mentions result reporting. The absence of an output schema is mitigated by noting that the result reports rejection. An agent has all necessary information to call and react.

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% – both parameters have clear descriptions ('New complete value for the field', 'Text field to set, from get_app_state'). The tool description does not add meaning beyond the schema; it merely rephrases that the field's entire contents are replaced. Baseline 3 is appropriate.

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 opens with a specific verb ('Replace') and resource ('a text field's entire contents') plus the mechanism (via accessibility API, without keystrokes). It clearly distinguishes this from sibling type_text by contrasting the approach.

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?

Explicitly states when to prefer this tool over type_text ('for long values or when the field already holds text') and when to fall back ('if the field rejects it'), even naming the alternative path. This gives an agent concrete decision criteria.

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