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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructiveness, so the bar is lower. The description nonetheless adds real context: a hard cap of five results, the exact fields returned (category, logo, active ad count, page_id), and that no sign-in is required.

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?

Two tight sentences: purpose and result shape come first, the auth reassurance last. No redundant restatement of the title or the schema.

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 usefully enumerates return fields and the five-result cap, which is what an agent needs to decide whether the result set is sufficient. It could go slightly further on match semantics (partial vs exact name matching) and whether zero results is possible.

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?

Only one parameter, and the schema documents it fully at 100% coverage with a min/max length and an example ('Gymshark'). The description's phrase 'by name' merely restates that, adding no format or matching-semantics detail beyond the 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 and resource ('Search ... Meta Ad Library database for an advertiser or brand by name') and scopes the result set to up to five brand matches. It implicitly distinguishes itself from tracked-brand siblings by naming the Meta Ad Library database as the source, but never names an alternative directly.

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 description makes the lookup intent clear (find a brand by name, get its page_id), but gives no explicit when-to-use/when-not guidance and does not point to search_tracked_brands, find_similar_advertisers, or compare_advertisers as alternatives. Usage is left to inference from the described return fields.

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