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

Annotations already declare readOnlyHint=true, destructiveHint=false, so the safety profile is covered. The description adds non-obvious behavioral context beyond that: the image reflects the real guest desktop and defines the shared pixel coordinate space used by the input tools, which is the critical fact for interpreting results. It omits freshness/timing (e.g., whether a delay is needed after an action before re-capturing).

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 short sentences with zero filler, and the core capability is front-loaded ahead of the coordinate detail. Nothing could be removed without losing 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 zero-parameter, non-destructive capture tool with no output schema, the description covers what is returned (an image of the guest desktop) and how its pixel space maps to other tools' inputs. The remaining gap is refresh/freshness behavior after prior actions, which is minor given the tool's simplicity.

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?

Zero parameters, so the baseline of 4 applies. The description correctly adds no parameter detail and instead spends its words on coordinate semantics, which is the relevant information for a parameterless capture tool.

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?

"See the real guest desktop" states the resource and action precisely enough for an agent to understand this captures a live view of the guest machine, and "this image" confirms an image is returned. It does not explicitly name a sibling, so differentiation from status is left implicit rather than stated.

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 coordinate sentence implies the intended workflow: capture this first, then feed pixel coordinates to click/move/scroll. However, it never states that guidance directly ("call before click"), nor when not to use it or how often to refresh, leaving the agent to infer the sequencing.

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