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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds a genuinely useful behavioral fact not in the structured data: Bing retains roughly six months of history, and the comparison window is fixed at 28 days vs the preceding 28. It does not discuss rate limits or result truncation beyond the schema's limit.

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?

Front-loaded with what is returned, then the parameter-routing guidance, then the sibling pointer — a sensible order with no filler. The first sentence is long and packs several distinct report sections, which slightly hurts scannability, but nothing is wasted.

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 does the job of describing returns (daily metrics, 28-day comparison, top queries/pages with impressions, clicks, average position) and adds a retention caveat. Combined with the 75%-covered schema for site/limit/page, an agent has enough to call it correctly; only permission/precondition details are absent.

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 75% and the `query` parameter has no schema description at all, so the description carries real weight here by explaining that `query` pivots to landing pages and `page` pivots to queries. That is meaning beyond the schema. It does not clarify the site-matching or limit interaction further, but the key ambiguity is resolved.

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 ('Bing search performance of a site') and enumerates exactly what is returned: daily impressions and clicks, 28-day vs prior-28-day comparison, top queries and top pages with impressions, clicks and average position. It explicitly positions itself against the sibling gsc_performance_overview, so an agent can distinguish the two without opening either 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?

Gives concrete routing rules for two parameters: 'Pass query to see the pages one query lands on, or page to see the queries one page gets', and points to gsc_performance_overview for Google data. This is clear usage context, but it never states when not to use the tool or what preconditions (e.g. a connected Bing site) are required.

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