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

Annotations already declare readOnly/openWorld/idempotent/non-destructive, so the safety profile is covered. The description still adds genuinely useful behavior no annotation conveys: untracked names are reported as not tracked rather than silently resolved to a lookalike, plus an explicit no-sign-in note and the shape of each comparison row.

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 sentences, front-loaded with the verb, scope, and output contents, with no filler. The trailing 'No sign-in needed' is slightly tangential given openWorldHint already signals public access, but costs little.

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 valuably previews the compared fields, and it clarifies the untracked-name edge case. However, with no required parameters and two alternative ID/name input paths, leaving 'page_ids' completely unexplained is a real gap an agent could trip on.

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 0%, so the description must carry both parameters, but it never mentions 'page_ids' at all and only alludes to 'brands' through prose about names. The stated '2 to 6' range also conflicts with the schema, which permits minItems 1 and zero required parameters.

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 (compare advertisers side by side) and enumerates the returned fields, so the agent knows exactly what the tool produces. The 'never replaced by a similar brand' clause implicitly separates it from find_similar_advertisers, but no sibling is named explicitly.

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?

Usage is only implied: 'tracked advertisers' signals a prerequisite (the brand must be tracked via track_brand first) and '2 to 6' bounds the input, but there is no explicit statement of when to prefer this over search_advertisers or find_similar_advertisers, nor when not to use it.

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