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

Annotations already establish a safe read (readOnlyHint, idempotentHint, destructiveHint=false), but the description adds real value beyond them: the return shape (per query the competing pages with clicks, impressions, share and position), the ordering ('biggest first'), and a plan gate ('Pro and Agency') that tells the agent about entitlement requirements.

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 tight sentences, front-loaded with the core concept, then return shape, then remediation, then tier. No filler; each sentence earns its place.

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 return-value burden and does so (per-query pages, metrics, ordering). All five optional params are fully schema-documented, so nothing an agent needs to call it correctly is missing.

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%, so all five parameters (days, site, min_share, include_brand, min_impressions) are already documented with defaults. The description adds no parameter syntax or format detail beyond the schema, so 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?

States a specific verb+resource with a precise detection definition: queries where two or more pages each capture a real impressions share and thus compete. An agent can distinguish it from gsc_search_analytics, gsc_opportunities and gsc_performance_overview without opening the schema.

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 implied by the tool's diagnostic nature and the remediation guidance ('fix by merging, differentiating or canonicalizing'), but it names no alternative sibling and gives no explicit when-to-use vs when-not-to-use condition relative to the other GSC tools.

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