Performance summary

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

readOnlyHint=true already establishes this as a safe read. The description usefully adds the comparative-period behavior (totals vs. an equal-length previous period), which the annotations don't convey. It says nothing about response size, row limits, or latency for large ranges, so it adds context but not a full behavioral picture.

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, front-loaded with the return content and closed with the routing hint. No filler, no 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?

With no output schema, the description must carry return-value burden, and it does outline the payload: totals, prior-period comparison, and top queries/pages. It is not fully complete — no indication of ordering, truncation, or what the comparison fields are named — but it is adequate for a 3-param, all-optional read tool.

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 100%: top, days, and siteUrl all carry their own semantics, defaults, and bounds in the schema. The description adds no parameter-level detail (e.g., how 'days' interacts with the comparison window) beyond what the schema already states, so the baseline 3 applies.

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?

The description names a specific output shape: period totals compared against an equal-length prior period, plus top queries and pages. That is concrete enough to distinguish it from a raw data-export tool, but it never names gsc_search_analytics, the obvious overlapping sibling, so the boundary is left implicit.

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?

'A good first call for "how is the site doing?"' gives an implied usage context and positions the tool as an entry point. It offers no when-not-to-use guidance and does not name an alternative for deeper/detail queries, so routing is only loosely implied.

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