browser_frame

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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds substantial behavior the annotations cannot express: the Linux unavailability, the prerequisite of an open browser preview with agent access, the ~6 s failure with the specific "no preview pane running" error, and the credential-page refusal pending user consent. This is exactly the preconditions-and-failure-mode context an agent needs.

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 load-bearing: what it returns, when to use it versus the sibling, and the environment/auth preconditions. The core action is front-loaded and there is no filler.

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 zero-parameter screenshot tool with no output schema, the description covers the return type (PNG image), the visual-vs-DOM tradeoff, platform limits, and the auth/failure conditions. Nothing needed to invoke it correctly 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 takes zero parameters, so the schema has nothing to document and the baseline of 4 applies. There is no parameter semantics for the description to add or omit.

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 ("Screenshot the preview as it renders right now") plus the returned artifact (PNG image). It explicitly differentiates itself from the sibling browser_dom, so an agent can choose between them without opening a schema.

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?

Gives concrete when-to-use cases (layout and visual bugs, result of a click) and names the alternative tool with the condition that selects it ("for exact sizes and styles use browser_dom"). It also states an availability exclusion ("Not available on Linux"), so the agent knows when not to call it.

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