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

Annotations only cover readOnly and openWorld, but the description adds substantial behavior: the credit cost model (1 credit/record, min 2), pagination ceiling (page × page_size ≤ 10000), and the important hidden-vs-genuine-zero semantics of the *_available flags. This is exactly the kind of context annotations cannot express.

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 purpose and mostly economical, but the sort enum is duplicated verbatim (once inline, once in a trailing 'sort:' clause) and page_size defaults are restated, which the schema already carries. Structure is good but that repetition costs it the top score.

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 22-parameter, output-schema-backed search tool, the description covers everything an agent needs to call it correctly: cost, pagination limits, sort defaults, hidden-count semantics, and provenance, while the output schema handles return values.

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 schema already documents parameters (baseline 3). The description goes further by explaining sort defaults (relevance with q, otherwise followers_desc) and the _available-flag relationship between stored 0 values and subscribers_count_available-style params, adding interpretive value beyond the raw schema.

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 (Searches) and resource (public YouTube channel profiles in a search index), and enumerates the record contents plus provenance (Common Crawl, Wikidata, About-page hydration). It also names the sibling datasets_youtube_creators_facets, letting an agent distinguish it from the facet/item siblings without opening schemas.

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?

Gives clear usage context: keep page_size to what you need because of credit cost, and route faceting to datasets_youtube_creators_facets. It lacks explicit when-not conditions (e.g., when to prefer datasets_youtube_creators_item or datasets_creators_search), so it falls short of a 5.

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