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

Annotations already establish the safety profile (readOnly, idempotent, non-destructive), and the description adds real behavioral context beyond them: it reports both API metric objects, states that differences are derived from the returned numbers, and documents the default comparison window when compare dates are omitted. This is meaningful disclosure for a read tool.

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?

Four short sentences, front-loaded with the core purpose and scope before the default-behavior detail. Slightly dense but no filler; 'Reports both API metric objects' borders on redundant given the output schema but still adds a useful hint about the shape of the comparison.

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 an output schema and full annotations present, the description needn't explain returns or safety, and it covers the comparison default well. But for an 8-parameter tool with 0% schema description coverage, the filter parameters (device, country, searchType) are left completely undocumented, which is a real completeness gap.

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% across 8 parameters, so the description must carry the burden, and it largely does not. It alludes to compareStartDate/compareEndDate via the default-window sentence and implies siteUrl via 'for a property', but device, country, searchType, startDate, and endDate are never explained in either place.

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 two date ranges using the Search Console totals for a property') and adds the scope qualifier '(no dimension grouping)', which implicitly distinguishes it from dimension-grouping siblings like top_queries and top_pages. It does not name a sibling explicitly, but the differentiator is clear.

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 final sentence 'Omit compare dates to use the previous window of the same length' gives a useful default-behavior cue for when compare params can be skipped. However, there is no explicit guidance on when to choose this tool over performance_trends or other comparison-capable siblings, so usage is only implied.

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