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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new behavior: results are ordered longest-running first and capped at the top 20, plus a 2-credit cost. It stops short of saying whether more than 20 results are reachable (pagination/truncation), which matters for an agent deciding whether one call suffices.

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?

A single compact sentence that front-loads the resource, then scope, ordering, cap, and cost. No filler or redundant restatement of the title.

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 one-parameter read tool with strong annotations and no output schema, the definition covers corpus, matching fields, ordering, result cap, and cost. The remaining gap is the fate of results beyond the top 20 and exact cost semantics, both minor.

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 0% and the single parameter is undocumented in the schema, so the description carries the burden. "By advertiser or copy" tells the agent what the query string is matched against, which is the key missing semantic. No format, length, or matching-operator guidance is given.

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 a specific verb and resource ("Search collected Meta (Facebook/Instagram) ads") and narrows the match surface to advertiser or copy, which separates it from the generic-sounding search_content sibling. It does not explicitly name a sibling or state the contrast, which keeps it off 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?

The phrase "by advertiser or copy" implies how to frame a query and the ad-specific corpus implies when to prefer it over a general content search, but no when-not condition or alternative tool is named. Usage is inferable rather than stated.

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