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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the "read-only ... changes nothing" sentence largely restates structured data. The credit cost ("Costs 1 credit per request") is genuine information not present in annotations and is the kind of budget constraint an agent needs, which raises it above baseline.

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 with the action front-loaded, followed by safety and cost. Nothing is padded or buried, and the cost note is placed last where it does not obscure the primary purpose.

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 one-parameter read tool whose safety profile is fully covered by annotations, the description covers purpose, mutability, and cost. The only material gap is what fields the returned user object contains, which matters more here because no output schema exists.

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 description coverage is 100% and the single uniqueId parameter is already documented with @ and full-URL examples. The description repeats "by username" but adds no syntax or normalization detail beyond what the schema supplies, so the baseline 3 applies.

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 a TikTok user by username") that maps one-to-one onto the tool name. It is distinguishable from tiktok_search_users by the "by username" qualifier, but the description never names that sibling or any of the tiktok_get_user_* tools, so differentiation is left implicit.

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?

Usage is only implied: an agent infers it should call this when it already has a username rather than a search query. There is no explicit "use this instead of tiktok_search_users" routing and no guidance on whether to follow up with tiktok_get_user_posts or tiktok_get_user_followers.

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