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

Beyond the sparse annotations, the description discloses meaningful behavior: it charges credits on create, refunds failed jobs, processes the whole clip in one pass, preserves the supplied audio, uses occlusion-aware lip sync, and returns a branded SwitchApp view_url. This adds real operational context that annotations do not provide.

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 four focused sentences with no filler. It front-loads the core purpose, then gives the workflow, behavior, and billing details. 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?

Despite having no output schema, the description is complete enough for an agent to invoke the tool correctly: it specifies the two actions, required inputs, sequencing, model constraint, return behavior, and credit/refund policy. The main missing detail would be the exact status response shape, but that is not necessary for correct invocation.

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 schema already has rich descriptions for all parameters, so the baseline is 3. The description adds value by clarifying the required create combination: video_url plus exactly one of sound_file or audio_url, and by confirming sound_file is a base64 data URI. This relationship is useful but mostly complements, rather than replaces, the schema's existing parameter documentation.

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 verb and resource: lip-syncing videos using Sync Labs Sync 3. It distinguishes itself by explicitly saying 'never Kling' and by calling itself the 'Main SwitchApp lip-sync', which helps differentiate it from sibling lip-sync tools. The create/status workflow is also immediately clear.

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 step-by-step usage: call action='create' with video_url and either sound_file or audio_url, then call action='status' with the returned task_id. It also excludes the Kling alternative and notes billing behavior, giving an agent concrete guidance on when and how to use the tool.

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