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

Adds real behavioral context beyond the annotations (readOnlyHint=false, openWorldHint=true): pricing ($0.75/GIF), a duration limit (up to 10s), and crucially the asynchronous contract (returns generation_id, must poll get_generation). This tells the agent the call is non-blocking and requires a follow-up, which annotations alone do not 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?

Three tight sentences, front-loaded with the core action, then pricing/limits, then the async contract. No filler; every sentence adds operational 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?

No output schema exists, so the description properly compensates by stating what comes back (generation_id) and how to retrieve the result. Combined with the annotation coverage of the safety profile, an agent has enough to invoke and follow up correctly, though the choice against sibling tools remains unaddressed.

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% and all three required params are documented in-schema, so baseline is 3. The description adds little per-parameter meaning (only the implied 10s GIF limit); it does not, for example, clarify the consent flag semantics beyond the schema.

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?

Specific verb+resource ("Swap faces in GIFs") that distinguishes it from siblings face_swap (images) and ai_face_swap_video (video) via the GIF medium. It does not explicitly name those siblings, but an agent can tell what this tool operates on.

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?

No explicit when-to-use vs alternatives guidance. It does give the follow-up workflow (call get_generation until status is "completed"), which is useful procedural context, but the choice between this tool and the many sibling swap/edit tools 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.