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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds the semantic that this is a differential analysis across two windows, but says nothing about output shape, pagination, or period-boundary semantics. With annotations carrying the safety burden, a 3 is appropriate.

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?

The two prose sentences are tight and front-loaded with the core action and value. The Args block repeats information largely already present in the schema titles, which is slightly redundant but aids readability for a 5-required-param tool. No padding beyond that.

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?

Covers required params with formats, states the read-only comparison intent, and there is no output schema so return values need not be described. Missing only edge-case semantics (overlapping periods, ordering of start/end values) and the unmentioned user_intent hint, which is a small gap.

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 17%, so the schema documents only user_intent explicitly; the description documents the five required params with date formats (YYYY-MM-DD). That compensates for most of the coverage gap, but the description omits user_intent entirely and gives no constraints such as baseline_end <= comparison_start. Baseline 3 reflects partial compensation.

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 ('compare visibility between two time periods') and elaborates what the comparison contains (how AI visibility changed between baseline and comparison periods). A sibling like compare_brands exists, but the description's 'two time periods' framing distinguishes this tool from that brand-vs-brand comparison well enough.

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?

Offers a use-case hint ('useful for measuring the impact of content changes or campaigns') which implies when to reach for it, but does not name alternatives like get_period_summary or compare_brands, nor any when-not-to-use condition. Usage is implied rather than directed.

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