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

Annotations provide readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=false, but the description adds substantial behavioral context beyond annotations: it details file format, dimensions, duration, codec, text rendering, music options, privacy (no AI, no watermark), storage lifecycle including deletion timelines per plan, return values, and rate limits. This is rich, non-obvious information that goes far beyond what annotations convey.

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 front-loaded with the core purpose and key constraints, then flows into behavioral details. It is somewhat long but every sentence adds value; no obvious repetition. Could be slightly more structured with paragraphs or bullets for readability, but acceptable as a dense block.

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?

Given no output schema and four parameters with full schema coverage, the description is highly complete: it covers what the tool does, output format details, return values (media_url, duration_s, text_on_video, message_for_user), lifecycle of the generated file, rate limits, and plan-specific differences. An agent has all needed information to invoke correctly.

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 description coverage is 100%, so baseline is 3, but the description adds meaningful context about how parameters affect output: text becomes heading and sentences, music can be royalty-free or silence, footer sits under the text, style options are light or dark. It enriches understanding beyond the schema descriptions alone.

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 a specific verb (makes) and resource (short vertical video) and names the target networks (YouTube, TikTok) where video content is required. It clearly distinguishes itself from sibling tools like post_to_social or schedule_post by focusing on video generation from text.

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 when to use this tool: for networks that take only video or video/photos, and it mentions the need to post or schedule soon due to deletion. However, it does not explicitly name alternatives or state when not to use this tool compared to siblings like generate_posts or replicate_top_post.

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