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

With readOnlyHint=true already provided in annotations, the description adds little behavioral context beyond the purpose. It doesn't mention pagination, rate limits, or timezone handling, but the annotation already covers the safety profile, so this is not a significant 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?

The description is a single, front-loaded sentence: 'Where visitors came from (referrer/source), with share of traffic.' It is concise, contains no redundant words, and immediately communicates the core purpose.

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?

Given the tool's simplicity, well-documented input schema, and read-only annotation, the description is adequately complete. It conveys the essential output concept (source breakdown with traffic share) even though no output schema exists. A slightly more detailed description of the response structure could improve it, but it is sufficient for the tool's complexity.

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?

The input schema has 100% description coverage, with all three parameters (site, limit, range) fully documented. The description itself adds no extra parameter-specific semantics, so it stays at the baseline of 3.

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 clearly states that the tool reports where visitors came from (referrer/source) with share of traffic. This specific resource type distinguishes it from sibling tools like get_geo, get_pages, and get_audience, which target different analytics dimensions.

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?

The description provides clear context for when to use the tool (when needing visitor source/origin data), but it does not explicitly mention alternatives or when not to use it. This is slightly below the highest level because it lacks direct exclusions or cross-references to sibling tools.

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