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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds useful provenance behavior not in the annotations: figures are sourced from each platform's own help/developer pages and each comes with a source link. Minor ambiguity in that the sourcing could read as live fetching while openWorldHint is false, but the phrasing most naturally means bundled provenance data.

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?

Two sentences, front-loaded with the data returned and then the trigger condition; nothing is padded. The platform list partially duplicates the enum values, which is the only small 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 one-parameter, read-only reference lookup with no output schema, the description covers what comes back (length, aspect ratio, resolution, source link) and when to call it. Pagination and edge cases are irrelevant here, so nothing material is missing.

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 100% and the single 'platform' parameter already documents the enum and the 'all' default. The description reinforces the platform scope but adds no format, case, or combination guidance beyond the schema, so baseline 3 applies.

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 names a specific resource (short-form video specs: max length, recommended aspect ratio, resolution) and enumerates the six platforms covered. An agent can immediately tell this is a reference lookup, not an editing-service or project tool like its siblings.

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?

"Use when someone asks how long a Short/Reel/TikTok can be or what size to export" gives a concrete trigger situation. It stops short of naming when not to use it or pointing at any alternative, but the sibling tools are unrelated enough that no ambiguity is likely.

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