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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=false and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-redundant context: the fixed result count (20) and the credit cost (1 credit), which is a real operational constraint an agent should weigh before calling.

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?

One sentence, front-loaded with the resource and source, then the return payload, then the cost. Every clause carries information; nothing is padding.

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 does cover the return shape (fields, count), which is the right call. However, for a tool whose two enum parameters are undocumented in both the schema and the description, the definition is incomplete on the input side.

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 33% — only 'country' is documented in the schema, and the two enum parameters (period, order_by) carry no explanation of what 7/30/180 or for_you/ctr/like mean. The description mentions 'for a country' but adds no semantics for period, order_by, or their defaults, so it fails to compensate for the coverage gap.

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 and source ('Top TikTok auction ads from TikTok Creative Center') plus the payload shape (20 ads with CTR, likes, budget tier, objective, video URL), so the agent knows exactly what comes back. It does not explicitly distinguish itself from the siblings (ad_radar_spy in particular could sound similar), so it stops short of a 5.

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?

Only 'Costs 1 credit' is offered as guidance; there is no when-to-use, when-not-to-use, or pointer to an alternative such as ad_radar_spy for competitor research. The agent must infer usage entirely from the name.

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