section_performance

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

Beyond readOnly/openWorld annotations it discloses two non-obvious behaviors: that results include share of clicks and a comparison against the previous period, and that domain (sc-domain) properties are split per host rather than aggregated. It does not say how truncation via top_n affects the delivered shares, which is the remaining behavioral gap.

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?

Two compact sentences, front-loaded with the metric and entity, no filler. The closing sentence about domain properties is terse to the point of being slightly cryptic about what 'split per host' means for the rows returned.

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 9-parameter tool with no output schema, the description covers the core metric but omits the default window, how top_n interacts with reported shares, and whether level or prefixes takes precedence. Enough to call it, not enough to call it correctly on the first try in edge cases.

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 78% and the schema already explains level, prefixes, dates and days well. The description adds the conceptual link between 'section' and the level/prefixes parameters, which helps an agent choose between them, but it says nothing about top_n, compare_previous, or precedence rules. Baseline 3 given the strong schema.

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 resource and scope: performance aggregated per site section, either a URL folder depth or custom prefixes, with click share and period-over-period change. That is clearly distinct from query-level or page-level tools, but no sibling (performance_query, performance_overview, query_segments) is named, so differentiation is left to inference.

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?

Usage is only implied by the aggregation unit ('per site section') – an agent can reason that this is the tool for folder-prefix rollups, but nothing states when to prefer it over performance_overview or compare_periods. No exclusions or prerequisites are given.

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