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

Annotations already declare openWorldHint=true, readOnlyHint=false and destructiveHint=false, so the description's job is to add operating context — and it does: 10-credit cost with refund on failure, plus the 'returns a download link' outcome. It doesn't cover link expiry, rate limits, or what a failure response looks like, which keeps it 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?

Three short clauses, front-loaded with what it does and what it returns, followed by the usage constraint and the cost. No filler or restatement of the title.

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 correctly carries the return value ('returns a download link'), and it disambiguates scope, cost, and accepted platforms for a one-parameter tool. Minor gaps remain around link lifetime and failure behavior, but nothing essential to a correct invocation is missing.

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 the schema already documents it at 100% ('Video link'), so the baseline is high. The description nonetheless adds real meaning by enumerating the accepted sources, which is not captured in the schema and directly affects whether the agent supplies a given URL.

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 (downloads) and resource (the video) plus the exact deliverable: a download link. Naming the supported platforms (YouTube, TikTok without watermark, Instagram, X, Facebook) makes it unmistakable against siblings like transcribe_video or create_clips, which consume video rather than return the file.

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?

Adds a clear usage condition — 'For the user's own or licensed content, or internal reference' — which tells the agent when the call is legitimate. It does not, however, route the agent to or away from specific sibling tools (e.g., use transcribe_video when text is needed instead), so an explicit alternative-routing sentence is missing.

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