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

With no annotations supplied, the description carries the full burden and does well: it discloses caching, the exact credit model (free first clip per character on Free, 50 credits unlocking all clips, none on Maker/Studio), and the return value (a download URL). It does not say whether the call is synchronous or requires polling via wait_for_job/list_jobs, which is a real gap for a potentially heavy render.

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?

Nearly all content earns its place, but it is delivered as one long run-on sentence with nested parentheticals, so the most important facts (what it downloads, cost, return value) are buried mid-string rather than front-loaded. Structuring the format list and credit rules as separate sentences would improve scanability without adding length.

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 an 8-parameter, no-annotation, no-output-schema tool, the description covers format tradeoffs, credit implications, caching, and the return value — enough to call it correctly. The remaining gaps are 'part'/'size' semantics and whether the export is asynchronous, which given the presence of list_jobs/wait_for_job siblings is a notable omission.

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 only 38%, so the description must compensate, and it largely does: it explains the clip values ('idle', 'breathing', 'sequence'), the meaning of the clips array, the optional matte colour for gif, and the background colour for mp4, plus per-format rationale. Undocumented are 'part' (full vs loop), 'size', and 'id', so a gap remains but the majority of ambiguous parameters gain meaning.

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?

Opens with a specific verb+resource ("Download a clip mascot's clip") and immediately enumerates the two clip modes ('idle'/'breathing' vs 'sequence' with clips [..]), which distinguishes it from the sibling export_mascot. The format list further pins down exactly what the tool produces.

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 use-case context ("for Slack, email or slides" for the sequence mode; Safari/Apple for hevc; apps and games for stacked-mp4), which implicitly guides format selection. However, it never states when to use this versus export_mascot, nor any prerequisites, so routing between siblings is left to inference.

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