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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful context that results are ranked by sessions, but says nothing about row limits per call, empty-result behavior, or attribution caveats. Adequate but not rich for a query tool with only annotation-level coverage.

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 short sentences with zero waste: the resource and ranking are front-loaded, and the routing hint follows immediately. Every clause earns its place.

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?

All parameters are optional with defaults, so an agent can call this with no arguments, and the description covers what the tool returns and when to prefer it. There is no output schema, but for a simple ranked list the semantics are self-evident; only a note on default window or result shape would fully close the 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 100% and each of the three parameters carries its own description and default, so the schema does the heavy lifting. The description adds no parameter-level meaning beyond it, making the baseline 3 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?

States a specific resource (the URLs that sent traffic) plus the ordering (ranked by sessions), so the agent immediately knows what comes back. It also explicitly distinguishes itself from list_traffic_sources, which prevents confusion with the channel-breakdown sibling.

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?

Gives an explicit selection rule: 'who is linking to us' routes here, while 'channel breakdown' routes to list_traffic_sources. The alternative and the condition that selects it are both named, leaving nothing to inference.

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