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

With no annotations supplied, the description carries the full disclosure burden and does real work: it states the cost (3 credits, cached or not), the refund policy on failure, the cache-skipping option, and the trial-credit restriction. What it omits is auth/permission requirements and rate-limit behavior, which keeps it short of a 5.

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?

Two sentences, zero filler. The identifier rule and the cost/refund terms are each stated once and front-loaded after the core purpose, so an agent gets the essentials in the first read.

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?

There is no output schema, so enumerating the returned fields is valuable and correctly present. Cost, caching and refund behavior are covered, and the 'exactly one of' rule closes the required-field gap. Only the absence of auth/prerequisite context keeps it from a 5.

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% and each parameter is documented, which would normally set the baseline at 3. However, the schema marks nothing as required (required: []), so the description's 'Give exactly one of `url` or `id`' supplies a mutual-exclusivity constraint the schema cannot express — genuine added meaning beyond the structured field.

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?

States a specific verb and resource ('Fetch one TikTok video') and enumerates the payload fields returned (description, username, create_time, duration, counts, sound, duet/stitch flags), so the agent immediately knows both the action and the shape of the result. It is cleanly distinguishable from the plural sibling get_tiktok_videos and from get_tiktok_comments.

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?

It gives one hard operational rule ('Give exactly one of `url` or `id`') and pricing/cache context, but never says when to choose this tool over get_tiktok_videos or search_tiktok. Usage is implied by the singular 'one' framing rather than stated as an alternative-selection rule.

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