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

No annotations are present, so the description carries the full burden. It discloses the Pro plan requirement, the need for pre-existing assets (video and character), and the async behavior (returns jobId, poll with status). It doesn't cover side effects or error conditions, but for a generation tool this is reasonably transparent.

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 sentences, front-loaded with the main purpose, followed by prerequisites and async flow. No fluff, every sentence earns its place.

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 7 parameters and no output schema, the description covers the essential flow: what it does, prerequisites, how to get the result (jobId + polling). It doesn't enumerate all optional parameters, but the schema already does that. Missing error handling details, but the core is 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 coverage is 100%, so baseline is 3. The description adds value by clarifying that videoUrl must be an uploaded RYLA video and that the character must already exist, which complements the schema. It also notes that outfitPrompt/backgroundPrompt are only used when their enabled flags are true, though the schema already says that.

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 states a specific verb and resource: 'Swap a character face into an existing video (face swap onto uploaded footage)'. It clearly distinguishes this from the sibling ryla_generate_face_swap (which likely targets images) by specifying 'existing video' and 'uploaded footage'.

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?

Provides explicit prerequisites: videoUrl must be an already-uploaded RYLA video, character must exist, and Pro plan is required. It also names the sibling ryla_list_characters for finding characterId and ryla_generation_status for polling. It doesn't explicitly state when not to use this tool, but the conditions are clear enough.

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