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

Beyond the annotations (readOnlyHint=false, etc.), it discloses fixed duration/resolution, a strict rejection behavior for non-480p requests, and a 75 MESH/call cost. It does not describe output representation or content-safety behavior, but the added constraints are meaningful for an agent.

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 operative sentence is front-loaded and clear, but the description also contains legal/category noise ("Powered by xAI. Not affiliated with or endorsed by xAI. (75 MESH/call, a tool · media)"). It is not excessively long, but not every sentence earns its place in a tool-calling description.

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 and only a generic input schema, the description must carry more weight. It omits the expected input payload structure and the return format, leaving an agent uncertain how to construct the call and what result to expect.

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 high, so the baseline is 3. The description adds that the input is 'a text prompt', but the schema's nested payload description is generic and mentions unrelated tools, so an agent still doesn't know the exact shape of the 'input' object (e.g., whether to pass {'prompt': '...'}).

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 uses a specific verb ('Generate'), names the resource ('1-3 second 480p video'), and scope ('from a text prompt'), with an explicit resolution constraint. This clearly separates it from image-generation siblings such as grok-image and grok-image-hq.

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?

It gives a clear usage context: short text-to-video generation at 480p only. 'Any resolution other than 480p is rejected' is an explicit when-not condition, though no sibling alternative is named.

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