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

Annotations already declare readOnlyHint and openWorldHint, yet the description adds genuinely new behavior: links are signed and expire after a few days, password-protected videos return 404, and each call costs 1 credit. That is useful context an agent could not infer from the schema or annotations, though throttling/rate-limit behavior beyond the credit cost is unstated.

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?

Tight, front-loaded sentences with zero filler: purpose first, then returned fields, then the two behavioral caveats and the cost. Every sentence 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 enumerates the return shape (including link ordering) and covers the main failure mode and cost. The only gap is the unexplained cache_max_age parameter, which leaves an agent guessing about caching behavior.

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 coverage is 50%; the url parameter is well documented in the schema itself as a video id or streamable.com URL, and the description adds nothing to it. The cache_max_age parameter is undocumented in both places, so the description does not compensate for the coverage gap.

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 resource (public Streamable video details) and enumerates the exact fields returned: title, duration, play count, upload date, thumbnail, and MP4 file links ordered tallest first. The platform-specific name plus field list makes it clearly distinct from generic siblings like vimeo_video or youtube_video.

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?

Usage context is implied rather than stated: it is for public Streamable videos, and password-protected ones return 404. There is no explicit guidance on when to pick this over other video tools or what to do when the call fails, and the credit cost is mentioned without framing it as a selection tradeoff.

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