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

With no annotations, the description carries the full burden and does so well: it discloses async execution, 1–5 min latency, credit cost per clip with exact per-model prices, and plan-tier gating (creator+/hobby+). It stops short of covering failure behavior, idempotency, or whether the render is cancellable, which are meaningful gaps for a credit-spending mutation.

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 operation, latency, and cost profile, then the routing instruction. The per-model cost/tier enumeration is long but each entry earns its place because model selection is gated on price and plan; it could be tightened into a table but no sentence is filler.

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-param, no-output-schema tool, the description covers the essentials: what it does, how long it takes, what it costs, and how to retrieve the result via get_video_status using the returned id. Minor omissions (cancellation, partial-failure handling) are tolerable given the absence of annotations.

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%, so the baseline is 3, but the description adds real decision value beyond the schema's vague 'Some models need a paid plan' by mapping each of the 16 enum values to a credit price and minimum plan tier. This directly informs the `model` parameter choice in a way the schema does not.

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 concrete verb+resource ('Start a video render') and immediately qualifies the operation as async with a 1–5 min duration. It is trivially distinguishable from siblings like generate_image, generate_music, and generate_speech.

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?

Explicitly states the follow-up path: 'If still processing when this returns, poll get_video_status with the returned id,' which names the sibling and the condition that selects it. It does not, however, contrast this tool against generate_image/generate_music for ambiguous 'make me media' requests, leaving that inference to the agent.

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