Screenshot

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

No annotations are provided, so the description carries the burden and does so well: it discloses that background tabs are captured without switching, that window size and viewport are never changed, and that full-page capture is impossible. It doesn't mention permissions or error behavior, leaving some gaps.

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 dense sentences, front-loaded with the core capability and then the constraint and fallbacks. Every clause earns its place with no repetition.

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 screenshot tool with no output schema and full schema coverage, the description is complete enough: it covers what is captured, the background-tab behavior, and the full-page limitation. It could mention the return format (image vs. path) but the schema covers parameters.

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 schema already documents all four parameters, including tab, slot, agent, and multiSlot. The description adds no parameter-specific meaning beyond the schema, so baseline 3 is correct.

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 (captures) and resource (visible area of the tab as PNG), and implicitly distinguishes itself from browser_pdf and browser_snapshot by naming PNG and the visible viewport. An agent can tell exactly what this produces.

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 says full-page capture is unsupported and routes to alternatives (scroll then capture, or use snapshot/text), which is clear when-not guidance. It doesn't name browser_pdf as the full-page alternative, so the routing is slightly incomplete.

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