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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, and the description reinforces rather than contradicts them. It adds genuine behavioral detail beyond the annotations: the 7-step progress model, the script appearing once written, and the MP4 URL only being returned when the final cut is ready.

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, front-loaded with the core action ('Check the progress...') before the return-value detail. The parenthetical listing what progress looks like is dense but earns its place; no filler sentences.

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?

An output schema exists, so return values need not be spelled out, yet the description usefully previews the two key outputs (progress state and MP4 URL). It also anchors the tool to the signed-in account. The only real gap is the unexplained project_id, which is minor for a single-parameter tool.

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?

There is a single required parameter, project_id, with 0% schema description coverage, so the schema does not explain it. The description never mentions project_id or clarifies whether it is the run/project identifier or where to find it, leaving the parameter's meaning to inference from its name.

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: 'Check the progress of a video ad run' and 'return the finished MP4 URL'. It also scopes the operation to the signed-in ManyMotions account and implicitly distinguishes itself from generate_ugc_video_ad and prepare_ugc_video_ad by being the status/retrieval counterpart.

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 description gives clear context for when to call it (polling progress, fetching the final MP4) and explicitly excludes write behavior with 'it never starts or changes a run', which steers the agent toward the sibling generate/prepare tools for those actions. It stops short of naming those alternatives directly, so the routing is implied rather than explicit.

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