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

With no annotations, the description carries the full burden and does well: it discloses the credit cost (3 credits regardless of cache), the refund policy for failed calls, and caching behavior tied to `fresh`. It omits auth/permission requirements and rate limits, but cost and failure semantics are disclosed where the schema alone would leave them hidden.

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 sentences, front-loaded with the resource and its return fields, followed by usage, constraint, and cost. The field enumeration is long but earns its place given there is no output schema; no filler sentences are present.

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 3-parameter, non-nested tool with no annotations and no output schema, the description covers returned fields, the input-exclusivity rule, usage intent, and cost/refund behavior. Only auth/prerequisite information is absent, a minor gap for a read-only profile lookup.

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%, so the baseline is 3; the description earns extra by stating the cross-parameter rule "exactly one of `username` or `url`", which the schema does not express (required is empty and there is no oneOf). It also notes the fields are "named as in TikTok's own APIs", clarifying the naming convention of returned data.

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+resource (fetch a TikTok account) and enumerates the exact fields returned, so the agent knows precisely what it gets. It is clearly distinguishable from siblings like get_tiktok_video, get_tiktok_followers, and get_tiktok_comments, which each target a different TikTok resource.

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?

"Use this for creator discovery and audience sizing" gives concrete intent, and "Give exactly one of `username` or `url`" supplies the selection rule between the two input modes. It does not name an alternative tool (e.g., search_tiktok for finding accounts you don't yet know), so it stops short of full when-not/when-else routing.

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