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

Annotations already declare read-only and open-world behavior, so the bar is lower. The description adds real value beyond them: the upstream data source (Creative Center, implying a different catalogue than the app feed) and the per-call cost of 1 credit. It stops short of describing pagination behavior or result volume, but the extra context is substantive.

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 short sentences, each earning its place: identity, scope/source, disambiguation, cost. Front-loaded and free of filler.

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?

With no output schema and five optional parameters, the description supplies the context an agent needs: what the data represents, where it comes from, and how it differs from the sibling trending tool. Only minor gaps remain, such as pagination expectations and the undocumented cache_max_age parameter.

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 80%, so parameters like period, region and count are already well documented in the schema. The description reinforces the notions of 'market' (region) and 'trailing window' (period) but adds no syntax, format, or defaulting detail beyond what the schema states. Baseline 3 is correct.

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 resource (popular/trending videos) plus the exact scope: videos trending in a market over a trailing window, sourced from TikTok's Creative Center. It also names the sibling endpoint tiktok_trending and explains how it differs, so an agent can distinguish the two without opening either schema.

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?

Explicitly contrasts this tool with /v1/tiktok/trending (personalised For You feed), which is the main selection ambiguity among siblings. It also discloses the credit cost, which informs invocation decisions. It doesn't discuss choosing between this and adjacent tools like tiktok_popularCreators or tiktok_hashtagVideos, but the core routing guidance is present.

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