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

Annotations already mark the tool read-only and non-destructive. The description adds value beyond annotations by defining the exact response shape and clarifying that 'visitors' means unique converters, 'events' means total conversions, and 'conversion_rate' is unique converters as a percentage of all visitors in the period.

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 description is front-loaded with the tool's purpose and then gives a compact, illustrative JSON example. The structure is efficient, though the inline JSON sample makes it slightly longer than necessary.

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?

There is no output schema, so the description carries full responsibility for explaining return values. It does so concretely with a result shape and definitions of each metric. Combined with the schema, all information needed to invoke the tool correctly is present.

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 100%, so the parameters (site, limit, period) are fully documented in the schema. The description adds no extra parameter semantics, but it does not need to; baseline 3 is appropriate.

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 states a clear resource ('the site's configured goals') and an operation ('ranked by conversions'). It distinguishes the tool from page/country/custom-event counterparts, though it does not explicitly name a sibling or boundary. The exact output sample reinforces the intent.

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 implied by the purpose: use this when you need goal rankings by conversion metrics. There is no explicit guidance on when to prefer this over siblings like top_custom_events or list_goals, nor any when-not-to-use conditions.

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