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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses fallback behavior for each view (local/nearby/elsewhere, sites, rules, ahead/behind, pages) and two concrete failure modes: a site with no meaning yet returns found/embedded false, and rules/content without `with` asks for it. It also states the authorization requirement ("Needs a key and a claim"), which annotations do not cover.

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?

Tightly front-loaded with labeled sections (When, Instead, Inputs, Returns, Fails) and no filler. However, some lines are compressed to the point of ambiguity, notably the Returns enumeration ("local, nearby and elsewhere; sites; rules; ahead and behind; or pages"), which costs a parsing pass it need not have.

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 takes on the return-value burden and does list the shapes per view, plus failure and auth conditions. The return enumeration and the phrase "kept reads" remain underspecified for a tool whose view-dependent output varies substantially, so a caller may still not know exactly what to expect from market or content views.

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 meaningfully exceeds the schema by explaining what each enum value means functionally — competitors as "rivals doing similar work", near as "closest in meaning", market as "rule by rule", rules/content as "two sites side by side" — whereas the schema only repeats the enum labels. It also clarifies `with` has a default interpretation (rules when used alone), information absent from 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?

The description conveys a specific verb and resource (compare a site against its rivals) and enumerates what the comparison yields: who the rivals are, how close they are, and where the site is behind. It also names the siblings it is not (clickd_leaderboard, clickd_site). The core action is stated somewhat metaphorically ("sets a site against", "from kept reads", "where it is behind"), so the agent must work a little to confirm the semantics, which keeps it off 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?

It gives an explicit "When:" clause (picking fixes that matter relative to the sites a buyer compares it with) and an explicit "Instead:" clause naming both alternatives plus the condition that selects each — leaderboard for rank among all sites, site for its own score. It also states the follow-up behavior for the rules/content views (supply `with`).

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