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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds useful behavioral context: data comes from 'our own archive' and persists beyond Google's window, plus the plan restriction. It does not describe output format, pagination, or update latency, but given the strong annotation coverage this is adequate.

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 deliver the core purpose, the key differentiator, and the access restriction with no filler. The most important information is front-loaded and 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?

For a read-only, two-parameter tool with fully documented parameters, the description is largely complete. It explains the data source, the time-window advantage, and the plan requirement. The lack of an output schema is partially mitigated by the phrase 'Traffic by month,' though a precise metric definition would make it fully complete.

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%, with both 'site' and 'months' already well documented, so the baseline is 3. The description adds no parameter-specific meaning beyond the schema; 'by month' aligns with the months parameter but provides no extra detail.

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 specific resource and action: 'Traffic by month from our own archive.' It also differentiates itself from Google-window-limited tools by noting it 'keeps going after Google's 16-month window closes,' which helps distinguish it from sibling traffic/performance tools. However, it does not explicitly name a sibling or clarify which traffic metric is returned, so it stops short of a 5.

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 this tool is valuable: when traffic history beyond Google's 16-month window is needed. It also notes the Pro and Agency plan restriction. It does not explicitly state when not to use it or name an alternative, so it lacks an explicit exclusion.

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