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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuine behavioral context beyond that: the window ends yesterday, output is capped, and rows include key events and a source-group breakdown (search, ai, social). Return shape is only partially characterized, but for a read-only analytics tool this is solid.

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 dense sentences, front-loaded with the resource and metric, with no filler. The "top 50" claim is the one phrase that costs clarity because it conflicts with the limit parameter's documented max of 200.

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 carries the burden of describing returns and does so at a useful level: sessions-ordered landing pages, key events, and a source-group split. It stops short of stating the response envelope or whether zero-traffic pages are omitted, which leaves minor gaps for a metrics 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 coverage is 100% and the schema already documents days (default 28, 7-90), limit (default 25, max 200) and project_id, so baseline 3 applies. The description adds little parameter meaning and in fact introduces a tension: it advertises "top 50" while limit allows up to 200, which could confuse an agent about how many rows it can actually request.

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 concrete resource (landing pages) plus the metric that orders it (sessions) and the extra dimensions returned (key events, source-group split of visits), which separates it from gsc_top_pages and ga4_traffic. It does not explicitly say how it differs from ga4_sources or ga4_traffic, so sibling differentiation is only partial.

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?

"Pair with gsc_page_queries to see what a page ranks for" gives a clear complementary-tool cue for a real workflow. There is no when-not guidance (e.g., when to use gsc_top_pages instead for rank-ordered pages), so the routing advice is helpful but one-sided.

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