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

Annotations already declare readOnlyHint=true and destructiveHint=false, so 'Changes nothing' largely restates the structured data. The description does add genuine behavioral context beyond annotations: the result is computed as a comparison against the same number of preceding days, and site-wide totals aren't derivable by summing per-query rows.

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?

Three tight sentences that front-load the metrics and the comparison, with no filler. The dash-free compressed style is dense but every clause carries information about what is returned.

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: it names the four metrics and the change versus the prior window. Read-only safety is covered by annotations, and the parameter space is covered by the schema, so nothing an agent needs 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 the schema fully documents days, fresh, start_date, end_date and site_url, including formats and the 3-day lag. The description's 'over a window' adds only a vague gesture at the time parameters and no meaning beyond the schema. Baseline 3 is appropriate.

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: total organic Search clicks, impressions, CTR and average position for a site over a window, plus prior-period comparison. The phrase 'Site-wide totals, more complete than adding up per-query rows' implicitly distinguishes it from the per-query performance tool, though it never names that sibling 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 implied – reach for this when you want site-wide totals and a period-over-period change rather than per-query detail. There is no explicit when-to-use/when-not statement and no alternative tool is named, so the agent must infer the routing against search_console_performance and search_console_trend.

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