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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds useful behavior that annotations do not: results are sorted by spend and unmapped spend appears under a null website id. It does not cover pagination, result volume, or what the response rows contain.

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?

A single front-loaded sentence with the read marker and scoping first, then the sorting and null-handling caveats. Dense but every clause carries information; only the redundant "[read]" prefix against readOnlyHint is wasteful.

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?

For a 10-parameter analytics tool with no output schema and no per-parameter descriptions, the description covers the core filtering semantics and the notable null-website edge case. It leaves gaps on the provider and campaign_key parameters, date formats, and result shape, which matter for correct invocation.

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% across 10 parameters, so the description has to carry the load. It does meaningfully explain that the website, account and customer filters accept either an id or a uuid, which resolves the id/uuid parameter pairs, and it gives since/until meaning as a date range. However provider and campaign_key are unexplained, and no date format is given.

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: reading ad performance per branch website for a date range, which distinguishes it from the campaign/summary/timeseries siblings. It stops short of naming those siblings or stating the boundary explicitly, so an agent must infer the distinction.

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?

There is no when-to-use vs when-not guidance and no mention of the alternative ads_insights_* tools. The date-range scope implies a reporting use, but nothing tells the agent when to prefer this over ads_insights_campaigns or ads_insights_summary.

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