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

The annotations provide only generic flags (readOnlyHint=false, destructiveHint=false, etc.), so the description carries the behavioral burden. It adds useful context beyond the annotations by disclosing that results are scanned and that the service enforces SFW/content restrictions. It does not mention return format or async behavior, but the added moderation and policy context is meaningful.

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?

The description is two tightly written sentences with no filler. The core purpose is front-loaded, and the second sentence delivers the necessary safety and legal guidance. Every clause adds value.

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 tool with only two string parameters, the description covers the core operation, the output expectation ('swaps the face'), and important usage constraints. It lacks explicit mention of return value shape or whether processing is asynchronous, but the tool is simple and the schema is well-documented, so the description is reasonably 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?

The input schema already documents both parameters clearly: baseImageUrl is the scene image and swapImageUrl is the face image. Since schema description coverage is 100%, the tool description adds no additional parameter-level meaning; the baseline of 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 clearly states a specific action ('Swaps the face') and the resources involved ('from one image onto another'), making the purpose immediately understandable. It does not explicitly differentiate from sibling tools like fattly_actor_swap, so it lacks the explicit sibling distinction needed for a 5.

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?

The description gives explicit usage constraints: SFW-only, rights-required, and no misleading/explicit imagery. However, it does not say when to prefer this tool over alternatives such as fattly_actor_swap or other image editing tools, leaving sibling-selection guidance implied rather than stated.

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