Capture a screenshot

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered without description help. The description still adds real context the annotations don't: the underlying command (`exec-out screencap -p`) and the return format (PNG image). It does not cover behavior with multiple devices connected, but the schema does.

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, zero padding, with the core action and return type front-loaded and the sibling routing held for the second sentence. Every clause earns its place.

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 single-optional-parameter read tool with full schema coverage and safety annotations, nothing an agent needs is missing: the action, the output format, and the alternative tool are all stated, and no output schema exists that the description would need to compensate for.

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% and the single `device` parameter is fully documented in the schema, so the baseline of 3 applies. The description only implies single-device scoping ('one device') and adds no syntax or format detail beyond what the schema provides.

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 ('Capture the current screen') plus the exact output artifact ('return it as a PNG image'), and distinguishes itself from the sibling get_ui_hierarchy by contrasting pixels vs. element coordinates. An agent can route between the two without opening either 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?

Explicitly names the alternative and the condition that selects it ('Follow up with get_ui_hierarchy when you need element coordinates instead of pixels'), which is genuine routing guidance. It doesn't state the inverse case (prefer screenshot when visual appearance matters) or note when-not to use it, so it falls just short of fully explicit.

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