compare_periods

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint, so the safety and idempotency profile is fully covered. The description adds little behavioral context beyond this — it does not describe the returned comparison shape (deltas, ordering) or any rate/quota behavior. With annotations carrying the safety burden, a 3 is appropriate.

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 sentences, each earning its place: capability, when-to-use, and the routing alternative. Front-loaded with the primary action and no filler.

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?

No output schema exists, but the description names the compared metrics and grouping option, and annotations cover the safety profile. It is nearly complete for a read-only comparison tool; only the shape of the returned comparison is unspecified, a minor 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 100%, so every parameter including the four date fields and the dimensions enum is already documented in the schema. The description's 'optionally grouped by a dimension' merely restates a schema-declared option without adding syntax or meaning. Baseline 3 is correct when the schema does the heavy lifting.

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 (compare) plus the exact resource (Search Console clicks, impressions, CTR, position) over two explicit date ranges, and names the sibling it is not (get_performance_summary). An agent can distinguish it from the other analytics tools without opening a 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?

Explicitly says when to use it ('when the user names a before and an after, such as a release or a season') and names the alternative with its own selecting condition ('latest period against the one just before it, without choosing dates'). Nothing is left to inference.

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