Fill

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

With no annotations, the description carries full burden. It states the basic behavior (fills an input, replaces value) but omits details like whether the field is cleared first, what events fire, error handling (element not found, not an input), or interaction checks (visibility, scrolling). 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?

Two compact sentences, no filler. Each word serves a purpose. Well-structured for quick reading by 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?

Tool has 10 parameters, no output schema, no annotations. The description is only 10 words long. It lacks return behavior, error conditions, prerequisites, and integration steps (e.g., need an open page). Incomplete for safe, correct invocation.

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 description coverage is 90%, so baseline is 3. The description adds minimal value beyond the schema—it clarifies that either 'selector' or 'snapshotRef' is used for targeting. No other parameter insights are provided. Does not significantly enhance understanding of the parameters.

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 action (fill), the target (input), and the methods (CSS selector or snapshotRef). It also notes 'Replaces existing value,' which distinguishes it from sibling tools like dev_browser_type (which likely appends). This meets the specific verb+resource+distinction standard.

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?

No explicit guidance on when to use this tool versus alternatives (e.g., dev_browser_type, dev_browser_click). No prerequisites mentioned (e.g., page must be loaded, element must exist). The description does not offer any usage context or exclusions.

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