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

Annotations only declare the safety profile (non-read-only, non-destructive, non-idempotent, closed-world). The description adds real behavioral context beyond that: output is a rendering status rather than a finished video (async), existing photos are preserved, brand text inherits saved brand settings, and account defaults must not be changed. These are exactly the operational facts annotations cannot 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?

Front-loaded with the core action and constraints, and every sentence carries information. However, the trailing clauses about brand settings, fonts, and account defaults read as guardrail instructions rather than tool documentation, giving the text a slightly scattershot feel for its 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?

With no output schema and 0% schema description coverage, the description does the heavy lifting, including clarifying the return value is a status. It omits how to retrieve the finished render (e.g., via the generation-status tool) and leaves one parameter undocumented, so it is strong but not fully complete.

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 0%, so the description must compensate, and it largely does: it documents the 2-12 photo count, the ordering semantics (not expressed in the schema), the targetSeconds 5-60 range, and the music/text defaults. The 500-char 'description' parameter goes entirely unexplained, which is the main gap.

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?

States a specific verb and resource ('Assemble 2-12 uploaded photos into a video') plus the key constraint that each photo appears exactly once in the supplied order. It also implicitly distinguishes itself from trend-based siblings ('uses the normal video renderer, not a trend sound') and from carousel tools, so an agent can route correctly.

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?

Clearly frames the tool as the non-trend renderer and notes the defaults (silent, text-free reel) and the 2-12 photo envelope, which tells the agent when this tool applies rather than create_from_trend or create_photo_carousel. It stops short of explicitly naming the alternative tools or stating when NOT to use it.

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