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

Annotations already declare non-readonly, non-idempotent, non-destructive, open-world behavior. The description complements them with the upload URL constraints and the confirm=false/true preview semantics, which are behaviorally useful. It does not delineate failure modes (what happens to a rejected upload or invalid URL), so it stops short of a 5.

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-loaded with the action and return value, then the URL caveat and the sibling alternative, then the confirm semantics. Information-dense with no filler, though the middle clause is a long run-on sentence.

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 needn't be explained, yet the description still notes video_id's role. Combined with annotation coverage and the URL/confirm guidance, an agent has enough to call it correctly; only advertiser_id semantics and error behavior are unaddressed.

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%, so the description must compensate. It explains video_url (must be a direct file, not a web page) and confirm (preview vs upload), but leaves advertiser_id and file_name undocumented anywhere, so the coverage gap is only partially closed.

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 (uploads a TikTok video creative from a public URL) and names the downstream consumer (create_tiktok_ad) plus the returned artifact (video_id). It clearly distinguishes itself from sibling tools that create ads from posts.

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?

Explicitly contrasts this tool with the alternative: 'a tiktok.com post link is a web page, not a file — to advertise an existing post use create_tiktok_ad with tiktok_item_id (list_tiktok_posts).' It states the precondition (URL must point at the file itself, .mp4/.mov) and the preview-vs-commit switch.

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