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

Annotations already declare write (readOnlyHint=false), non-idempotent, non-destructive, open-world behavior. The description adds genuinely new context — this returns an async job rather than a finished video, and consumes 'seconds' of quota — but the 'seconds' phrasing is cryptic and it never says whether re-invoking spawns a duplicate job or that vids_get_job is needed to retrieve the result.

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?

Three short sentences with the core action front-loaded and no filler. The middle sentence ('Uses the clip's seconds again') is too terse to parse confidently, and the trailing 'POST /videos/upscale' is endpoint trivia an agent cannot act on.

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 one-parameter, no-output-schema tool this is close to adequate: the async job nature is stated and the input constraint is implied. It falls short by not naming the polling tool or clarifying the quota language, which an agent needs to actually complete the workflow.

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?

Only one parameter and schema coverage is 100%, so the schema already documents mediaId fully, including that it must come from a finished video job's result. The description's '720p clip' adds no meaning beyond the schema. Baseline 3 applies when the schema does the work.

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+resource with concrete constraints: 'Turn a 720p clip of up to 20 s into 1080p.' An agent immediately knows the operation and its input bounds. It does not explicitly differentiate itself from siblings like vids_edit_video or vids_extend_video, which are the nearest alternatives.

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?

Usage is only implied: 'A job, like vids_create_video' signals the async-job pattern and 'Uses the clip's seconds again' hints that quota/credits are consumed, but there is no explicit statement of when to choose upscale over edit or extend, nor any stated prerequisite beyond the schema's 720p requirement.

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