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

The description mentions 'Billing per call: 1 Credits' and the group, but does not disclose behavioral aspects such as whether the tool is read-only, if it makes network calls, or any side effects. Since no annotations are provided, the description carries the full burden, and it is minimal. The description is simply a data type explanation, not a behavioral disclosure.

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?

The description is concise and uses markdown bold for the object type, which helps scanning. It is only a few sentences and front-loads the key information (map of thumbnails). The inclusion of 'Group' and billing info adds some extra but is relevant context, so it earns its place.

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?

The tool has a simple parameter set and schema coverage is high, but the description fails to explain what the thumbnail data might include (e.g., sizes, URLs) or what the return format will be. Since there is no output schema, the description should guide the agent on what to expect, but it only says 'other information' without specifics. For a tool with one param and no output schema, this is below par.

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?

The schema already provides complete coverage of the only parameter 'id' with a detailed pattern and example, so the description does not need to add much. However, the description does not explicitly connect the 'id' parameter to the video being queried, but the schema's example makes it clear. Baseline of 3 given high coverage, and the description's mention of 'video' provides mild additional context, so a 4 is justified.

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?

The description states that it returns a map of thumbnail images, but it is phrased as a definition of the object rather than a clear action. The verb is missing; it reads as '**object** A map of thumbnail images...' rather than 'Returns a map of thumbnail images...'. It does distinguish the resource (thumbnails) but not clearly from the sibling 'get_mux' or other info-getters, and the title adds little.

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?

There is no guidance on when to use this tool versus alternatives. It is in the group 'Specific video Info' and requires a video ID, but there are no explicit instructions or exclusions. The context of 'Group: Specific video Info' is present in the description but is not actionable guidance for choosing this over siblings like get_info or get_mux.

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