type

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

There are no annotations, so the description carries the behavioral burden. It discloses the append behavior and the 90s timeout, but it does not describe error cases, return values, or side effects beyond modifying the input. This is adequate but not rich.

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 concise sentences: the primary action, routing to alternatives, and the timeout constraint. Every sentence earns its place and the most important information is front-loaded.

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 primitive input-action tool with a well-documented schema, the description provides the essential usage context, timeout, and sibling disambiguation. It does not describe output/return behavior, but that is arguably less critical for an action command.

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 schema already documents all parameters. The description adds the important semantic that text is appended rather than replacing, but it does not add detail about the other parameters such as delayMs or device selectors.

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 action and resource: 'Append text to the currently focused input.' It clearly distinguishes itself from the siblings fill and focus, so an agent can tell this tool apart without ambiguity.

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 explicitly provides routing guidance: use fill when replacing, use focus first when no input is active, and use type when appending to an already focused input. This covers the key alternatives and the condition for choosing this tool.

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