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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), and the description adds genuinely new information: the returned payload includes SD and HD MP4 with audio, separate video/audio tracks, thumbnail, title and duration. It does not disclose failure modes for non-public URLs or whether the links expire, 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?

A single sentence with zero filler, front-loading the action and resource before the output enumeration. Every clause carries information an agent needs.

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 usefully summarizes what comes back, which is the main gap it needed to fill for a one-parameter extraction tool. The omission of error behavior for private or invalid URLs is a minor remaining gap given the simplicity of the 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?

With one parameter and 100% schema description coverage, the schema already documents the url field. The description adds marginal value by widening the accepted URL forms to reel, watch, share and photo post links, but adds no syntax, format or validation detail beyond the schema example.

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 (get direct download links) and a specific resource (public Facebook video, reel, watch link, share link, or photo post), then enumerates the returned formats. An agent can tell this apart from pinterest_download_links and tiktok_download_links purely by the platform named in the same sentence.

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 word 'public' establishes a real precondition and the enumerated URL types tell the agent what inputs qualify. There is no explicit statement of what happens with private or deleted content and no alternative tool is named, but the sibling tools cover different platforms so no routing ambiguity exists.

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