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

Goes well beyond the readOnly annotation: it discloses the Free-vs-Pro data availability split and pins down the window semantics as the last N days ending today in UTC, explicitly excluding calendar week/month interpretations. It also names the returned fields and the top-10 caps.

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?

Front-loaded with purpose, then constraints, then return contents — a sensible order. Dense but nearly every clause carries operational information; the final enumeration sentence listing topLinks/topChoices/topRoutes runs long but is not padding.

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?

With no output schema, the description does the work of describing the return shape (totals, busiest days, top devices/countries/referrers, topLinks, topChoices, topRoutes) plus echo fields from/to/days/timeZone. Only edge behavior such as what happens with an invalid slug or zero data is unaddressed.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning to `days` by defining the window as rolling N days ending today in UTC rather than a calendar period. The `slug` usage is also restated in terms of scope, which is only mildly additive over the schema.

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?

Opens with a specific verb+resource (click statistics) and states the two scopes: all links, or one link via "slug". An agent can distinguish it from get_link or find_links because the output is explicitly aggregate metrics rather than link records.

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 clear selection criteria for the optional slug (all links vs one link) and sets expectations about plan tiers, noting that per-day/country/device/referrer breakdowns require Pro. It does not name a sibling alternative or state when not to use it, so it stops short of an explicit routing rule.

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