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

Annotations already declare destructiveHint=true and openWorldHint=true, so safety is covered. The description adds genuinely new operational context: only one recording at a time, an 8192 MiB per-sandbox retention cap, and automatic stop before the disk fills. These constraints are useful and not derivable from the structured fields.

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?

Front-loads the core purpose, then the action workflow, then constraints, with no redundant sentences. The semicolon-heavy telegraphic style is dense but every clause carries distinct 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?

With no output schema, the description appropriately explains what start returns (a recording id) and how to retrieve the finished file. For a 7-parameter, four-action tool the coverage is solid, though it could briefly note default behaviors per action.

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 coverage is 71% and crf/fps/maxMiB/maxSeconds already carry schema descriptions, so the schema does much of the work. The description nonetheless adds meaning by mapping action values to parameters (start returns an id; stop/delete take recordingId), clarifying the otherwise opaque enum-to-argument relationship.

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?

Names a specific verb (record) and resource (a sandbox's desktop to an MP4 file), clearly distinguishing it from siblings like runtime_sandboxes_desktop_screenshot and runtime_sandboxes_desktop_act. An agent knows immediately this tool captures desktop video rather than a still frame or input 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?

Describes the multi-step workflow precisely: start returns a recording id, stop (recordingId) finalizes the file, and list/delete round out the actions, plus the exact fetch command for download. It stops short of stating when to prefer this over the screenshot sibling, but the action semantics give clear usage context.

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