Grok MCP

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

With no annotations provided, the description carries full burden and does well by explaining key behavioral aspects: the tool creates a seamless continuation, duration applies only to the extension (not total output), and it returns a Markdown block with URL and duration. It doesn't mention rate limits, authentication needs, or error conditions, but covers the core operation thoroughly.

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 efficiently structured with purpose first, then key behavioral clarification, followed by well-organized parameter and return sections. Every sentence adds value: the example clarifies duration behavior, and the Args/Returns sections provide essential information without redundancy.

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?

For a 4-parameter mutation tool with no annotations and no output schema, the description does an excellent job covering the core operation, parameters, and return format. It lacks some contextual details like error cases, rate limits, or authentication requirements, but provides sufficient information for basic correct usage.

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 0% schema description coverage, the description fully compensates by providing detailed parameter explanations in the Args section. Each parameter gets clear semantics: prompt describes content, video_url specifies format constraints (.mp4, 2-15s), model gives default, and duration explains range and behavior with a concrete 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?

The description clearly states the specific action ('Extend an existing video with a follow-up prompt') and resource ('video'), distinguishing it from sibling tools like generate_video (which creates new videos) and other unrelated tools. The first sentence provides a complete purpose statement with verb and object.

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 description implies usage context by specifying it continues from an existing video's last frame, which differentiates it from generate_video. However, it doesn't explicitly state when NOT to use this tool or name specific alternatives, though the distinction from generate_video is clear from the purpose.

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