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

With no annotations, the description carries the full behavioral burden and mostly does: 3 credits whether cached or not, failed calls refunded, cache-skipping behavior, and the Europe-only geographic limit. It does not state whether results are ever stale beyond the cache note, but the cost/refund/scope disclosures are substantive and non-obvious.

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?

Front-loaded with the core action and corpus, then fields, then cost/scope. The field enumeration is long but each item is load-bearing since there is no output schema. No filler sentences.

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?

Compensates for the absent output schema by listing the ad attributes returned and the page size, and covers cost, refunds, and region. Auth requirements and rate limits are not addressed, but for a keyword-search tool the agent has what it needs to call 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 description coverage is 100%, so query, cursor and fresh are already documented in the schema; baseline 3 applies. The description adds only marginal meaning, mainly "about 12 a page" which contextualizes the cursor, plus keyword-scoping for query.

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 (search TikTok's public Ad Library by keyword) and enumerates the ad fields returned, which distinguishes it cleanly from search_tiktok (organic videos) and search_linkedin_ads. An agent can tell exactly what corpus is being searched without opening the 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?

"Use this to watch what a brand or a category advertises" gives clear intended context, and the Europe-only scope narrows applicability. It stops short of naming an alternative (e.g. search_tiktok for organic content) or an explicit when-not-to-use condition, so it misses the top band.

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