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

Annotations already declare this is a non-read-only, non-destructive, open-world write, so the safety bar is lower. The description adds real behavior beyond that: the source must be a publicly reachable direct link, accepted formats and aspect ratio, duration bounds of 5–60s, and the fact that a video_id is returned for reuse. It omits whether re-uploads duplicate assets or how long ingestion takes, which keeps it at 4 rather than 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?

Three tight sentences, front-loaded with the action and source, then the return value, then the alternate input. Every clause carries information an agent needs; nothing is padding.

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 6-parameter write tool with no output schema, it covers the inputs, the media constraints, and the return value (video_id). The one real gap is that required is empty in the schema and the description never states that exactly one of video_url or media_id must be supplied, which could let an agent fire a contentless call.

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?

At 67% schema coverage the schema does part of the work, but the description meaningfully enriches the two consequential parameters: video_url must be a direct public MP4/MOV link with 9:16 framing and 5–60s length, and media_id traces back to an [attachment …] marker in the Go Shift chat. folder, account, language and file_name get no narrative treatment, leaving a gap but not an ambiguous one.

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?

Specific verb plus resource ("Upload a video to the advertiser's TikTok asset library"), with the accepted sources made explicit and the downstream consumers (tiktok_create_campaign / tiktok_create_ad) named. An agent can immediately distinguish this from meta_upload_video or snapchat_upload_media as the TikTok-platform uploader.

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?

Clear guidance on which input path to use: a public https URL, or media_id when the file was attached in the chat ("Use instead of the URL"). It also signals this is a preparatory step for the create-campaign/create-ad tools. No explicit exclusion or prerequisite statement (e.g. account permissions, what to do if the upload fails), so it stops short of a full when/when-not treatment.

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