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

Annotations already mark this as read-only, and the description adds valuable behavioral details: missing captions result in an error, and successful requests including cached ones cost 0.2 credits. This goes beyond the structured annotations and helps the agent anticipate failure modes and cost.

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 three short sentences, all substantive. It front-loads the core behavior, then covers error cases and cost without any fluff or repetition of the tool name.

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 single-parameter, read-only tool with an output schema, the description is largely complete: it states the action, error behavior, and cost. It could be slightly more explicit about the relationship to transcript tools, but the essentials for correct invocation are present.

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?

There is only one parameter, 'url', and the schema provides a URI format but no descriptive text. The description does not add any semantics about what URL should be provided, though the parameter name and format are fairly self-explanatory. Schema description coverage is 0%, so the description could have compensated more explicitly.

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 the action ('Fetch available captions') and the resource ('TikTok video captions'), and explicitly distinguishes it from transcript generation by saying 'without generating a transcript.' This differentiates it from sibling tools like get_tiktok_video_transcript and get_tiktok_video_transcripts.

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 phrase 'without generating a transcript' gives useful context for when this tool is appropriate versus transcript-generation siblings. It does not explicitly name alternatives or state when not to use it, but the implication is clear enough for a simple fetch tool.

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