browser_type

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

Annotations already indicate this is a destructive, non-read-only action. The description adds valuable behavioral context by explaining that it sets the value rather than typing, so it does not fire per-keystroke handlers. This is a key behavioral trait beyond what annotations provide, and it helps an agent understand side effects. It could mention more (e.g., blur events), but it adds solid 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?

The description is two sentences, front-loaded with the core action, and contains zero filler. It efficiently conveys the main purpose and the critical exception, making it highly scannable for an agent.

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 tool with 3 parameters (2 required) and an output schema, the description covers the primary behavior and the main alternative. It does not discuss error cases (e.g., selector not found) or prerequisites like element visibility, but these are minor given the tool's simplicity and the presence of an output schema. It is reasonably complete for an agent to invoke correctly.

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?

The input schema has only 33% description coverage (only the 'browser' param is described). The description does not explain the 'selector' or 'text' parameters at all, and the schema provides no descriptions for them. Since coverage is low, the description should compensate, but it does not. The agent must infer from names alone, which is insufficient.

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 clearly states the tool's function: 'Fill a field, replacing whatever it holds.' It uses a specific verb ('fill') and a clear resource ('field'), and it distinguishes itself from sibling tools by explicitly contrasting with browser_press_key, which types key-by-key. This makes the purpose unambiguous and differentiates it from related actions.

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 provides an explicit alternative and a condition for when NOT to use this tool: 'For those, click the field and use browser_press_key.' It implies the primary use case is when you want to set a value directly without triggering per-keystroke handlers. It does not list all possible use cases, but the exclusion is clear and helpful.

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