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

Annotations only say readOnlyHint=true; the description adds substantial behavioral context: avg_position is a rank (smaller better), negative delta means improvement, omitted buckets for pages not appearing in search, data lag of 1-2 days, granularity default behavior, and OAuth-dependent site_id optionality. This far exceeds the annotation baseline.

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?

Though ~150 words, the description is tightly structured: main function first, then parameter specs, then behavioral nuances, then sibling disambiguation. No redundant or filler sentences; every clause adds value, even the 'FD-040' reference hints at internal taxonomy without being misleading.

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?

Given the output schema exists, the description need not detail return fields, but it still mentions the series/summary shape and key fields. It covers all operational contexts: Google-search scope, default period, granularity override, OAuth behavior, and data gaps. No important usage aspect is left unaddressed.

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 0%, but the description explains every parameter in prose: page accepts normalized path or full URL, period defaults to '30d' with accepted values, granularity default and override rationale, and site_id optional under OAuth. This fully compensates for the missing schema descriptions.

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?

The description opens with a specific verb+resource: 'Return how ONE page's Google Search performance changed over time' and explicitly positions it as the 'time-axis drill-down' relative to get_breakdown(dimension='page'). It also distinguishes from get_keyword_performance for query trends, making sibling differentiation crystal clear.

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?

The description states exactly when to use this tool: 'Use this to verify whether SEO work on a page paid off (rank rose / clicks grew) or slipped.' It also gives explicit alternatives: 'for the cross-page snapshot use get_breakdown(dimension='page'), and for per-query (keyword) trends use get_keyword_performance.' No ambiguity.

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