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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered; the description adds genuinely new behavioral context by disclosing the billing rate ($0.006 per request) and the shape of the returned payload. It does not mention rate limits, caching, or behavior when a profile is private/deleted.

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 first covers input modes and the exclusivity rule, the second covers return contents and cost. Everything is front-loaded with no repetition of the name or title.

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, the description compensates by enumerating the returned fields (bio, bio link, follower/following counts, likes, video count, verification, join date, linked socials), and it also discloses cost and input constraints. An agent has everything needed to call and interpret this tool correctly.

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 the schema documents each of the three lookup keys with formats and length caps, so the baseline is 3. The description earns an extra point by stating the mutual-exclusivity rule ("provide exactly one"), a constraint the schema cannot express given required=0.

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 (get a TikTok user's profile) and enumerates the three lookup keys, so an agent immediately knows this is a direct identity lookup rather than a discovery call. It does not, however, explicitly differentiate itself from the sibling search_tiktok_users (that link only appears in the schema for user_id).

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?

"provide exactly one" is a concrete usage constraint that tells the agent how to call the tool, and the schema's user_id description ties it to search_tiktok_users as the upstream step. There is no explicit when-not-to-use guidance or statement of which sibling to prefer when the agent only has a display name or partial query.

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