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

Annotations cover the safety profile (non-read-only, non-destructive, non-idempotent), and the description adds two things annotations cannot: an expected latency ('a few minutes') and a legal/consent obligation. It stops short of saying whether credits are consumed or how to poll for the result.

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?

Three short sentences, each earning its place: what it does, how long it takes, and the consent condition. The core action is front-loaded with zero waste.

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?

The tool is a long-running job, but the description never says how the result is retrieved, for example through fattly_video_status. With no output schema, that retrieval path is a real gap, though the latency hint and consent note cover the rest.

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 all four parameters, including the required consent flag, are already documented in the schema. The description only restates the consent condition and adds no syntax or format detail beyond it.

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: 'Replaces the creator in an existing video with another actor.' An agent can grasp the operation immediately, though it does not disambiguate from the sibling fattly_face_swap, which sounds closely related.

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 conveys the cost of the operation ('takes a few minutes') and a legal precondition (likeness rights), but gives no explicit guidance on when to pick this over fattly_face_swap or fattly_edit_video.

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