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

Annotations already declare readOnlyHint and openWorldHint=false, so the bar is lower; the description still adds the per-call price, the fixed platform list, and the fact that outputs are cited with source and as-of date. It does not mention failure modes or what an empty filter result looks like, but the billing and provenance disclosure is the material detail.

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 compact clauses: price first, then what you get, then optional filters. No filler, front-loaded on the cost that gates usage.

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, describing the returned record shape (figure plus source report, URL, as-of date) is exactly the missing piece and is covered. Payment/auth is handled by the api_key schema field, leaving only minor gaps such as result granularity and empty-result behavior.

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 only 25%, so the description must compensate: it explicitly enumerates valid platform values (meta, google_search, google_display, tiktok, linkedin), which the schema leaves as an unconstrained string. It also confirms all three query parameters are optional filters, though it says nothing about industry vocabulary.

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?

Names the exact resource and metrics delivered ('CPM, CPC, CTR by ad platform ... and industry') plus the enrichment each figure carries (source report, URL, as-of date). No sibling tool covers ad benchmarks, so it is unambiguous against the catalog.

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?

The leading 'PAID $0.002 USDC' gives an agent the key cost consideration before calling, and 'Optional platform, industry, metric' implies filter narrowing. However, there is no explicit statement of when to use this versus a free alternative, nor any prerequisite or exclusion guidance.

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