Screenshot

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe read operation. The description adds useful behavioral context: the output is a JPEG, it can capture the full page or a specific element, and it is suited for visual checks. No contradictions with annotations.

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 sentences, front-loaded with the action and scope, followed by a clear usage directive. No wasted words; each sentence adds essential information.

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 tool with 7 parameters but only 1 required, the description explains the primary use case, the output format (JPEG), and when to avoid it. The element-selection details are fully covered by the schema. The description is sufficient for an agent to decide when to invoke the tool and what to expect.

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 100%, so the baseline is 3. The description mentions 'page or element', which loosely maps to the targeting parameters (css/ref/role/name/index), but offers no additional syntax or selection details beyond what the schema already provides. It neither gains nor loses points because the schema already fully documents 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 states a specific action ('captures a JPEG'), the resource ('the page or an element'), and explicitly scopes it to visual questions (layout, styling, rendering). It clearly differentiates from sibling tools like browser_snapshot and browser_read_text, making it easy for an agent to pick the right tool.

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 says 'Use this only for genuinely visual questions' and names two faster/cheaper alternatives (browser_snapshot and browser_read_text) for finding/verifying content. This provides unambiguous when-to-use and when-not-to-use guidance, with concrete alternatives.

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