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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds real value beyond them: a prerequisite (GSC must be connected) and tier-gated behavior (free = preview, paid = full results), which materially affects expectations.

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, front-loaded with the core comparison, then returns, then prerequisites. No filler, though the returns clause and the plan clause are packed into a rather dense final sentence.

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, so the description carries the return-value burden and does so (losers, gainers, position changes), plus it discloses the auth requirement and plan gating. Complete enough for an agent to call and interpret it, though it omits pagination/volume limits.

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 'days' param is already documented with range and default (7-180, default 90). The description reinforces semantics by framing 'days' as a comparison window, but adds little syntax or meaning 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 (Compare) and resource (Search Console performance), plus precise scope: last N days vs the previous N days. It names what it returns (biggest click losers and gainers with position changes), which cleanly separates it from siblings like get_search_console_keywords and get_search_console_cannibalization.

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?

Gives a clear use case ('spotting traffic drops and decaying pages'), which tells the agent when this tool is the right pick. It stops short of naming alternatives or explicit when-not-to-use conditions, so routing is inferred rather than stated.

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