browser_mark_screenshot

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

With no annotations, the description carries the behavioral burden and does well: it discloses that numbered boxes are drawn, that an image plus selector mapping is returned, and that refs feed into browser_click. It does not discuss limitations like full-page vs viewport capture, but the behavior is clearly conveyed.

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 no filler. The purpose is front-loaded and the next-step instruction is included without 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 parameterless tool with no output schema, the description fully covers what the agent needs: what is produced, what is returned, and how to proceed next. Nothing essential is missing.

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 tool has zero parameters and the schema already documents that there are no parameters, so there is nothing for the description to add. This matches the baseline for parameterless tools.

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 and resource: screenshots the viewport with numbered boxes over interactive elements, which is Set-of-Mark. This clearly distinguishes it from plain screenshot siblings like browser_screenshot and ties it to the interactive workflow.

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 instructs the follow-up action: use browser_click with the returned ref, e.g. e3. It implies when to use this tool (when a clickable element map is needed), but does not explicitly mention alternatives or when NOT to use it, such as when a plain screenshot suffices.

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