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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds meaningful behavior beyond that: the result is base64-encoded image bytes and the tool fails without a started desktop, which the agent needs to sequence calls correctly.

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, value and precondition front-loaded, with no filler. It is efficient; a brief clause on parameter format would not have hurt but the current length is defensible.

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?

With no output schema, the description usefully states the return type (base64 image data), and it notes the runtime prerequisite. However, for a two-parameter tool at 0% schema coverage it leaves parameter meaning undocumented, so it is only marginally complete.

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 0% for two parameters, so the description carries the full burden, yet it never explains the required 'id' (presumably the sandbox/desktop identifier) nor the 'format' enum (png/jpeg) even though the output format is mentioned generically. An agent cannot infer valid values for 'format' or what 'id' refers to from the description alone.

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 resource (a sandbox's desktop) and the output form (base64 image data), which is enough to distinguish it from siblings like runtime_sandboxes_desktop_act and runtime_sandboxes_desktop_record. It never uses an explicit verb, but 'screenshot' functions as the action.

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 a concrete precondition — the desktop must be started via runtime_sandboxes_desktop_act action start — naming the specific sibling and action needed to enable this tool. It does not state when to prefer this over related desktop tools, but the prerequisite guidance is unusually actionable.

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