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

Annotations already cover readOnlyHint=true and openWorldHint=false, and the description adds real value on top: it is free, it requires a key and a claim, and the 'Fails:' line warns rows stays empty until a lookup exists. It stops short of explaining what a 'claim' entails or how credits are consumed.

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?

Labeled sections (When / Instead / Inputs / Returns / Fails) with the core purpose front-loaded and no filler. Every line carries distinct information an agent needs, including the return field list that no output schema supplies.

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 compensates by naming the return fields (host, rows, credits, price, perDay, note) and by covering the auth prerequisite and empty-rows failure mode. Minor gap: 'needs a key and a claim' is asserted without saying how to obtain or verify either.

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 the single parameter is already documented as a domain such as example.com; the description's 'Inputs:' line restates the same example. With the schema doing the work, this is the baseline case.

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 verb and resource ('Lists what assistants were found to cite for a site, question by question') plus the scope constraint ('from lookups already made') and secondary output (credits left). It also explicitly separates itself from clickd_site by noting that page quality is not the same as being cited.

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 'When:' line gives the concrete decision context (tell a person whether assistants cite their site, at no cost) and the 'Instead:' line names the sibling clickd_site along with why it is the wrong choice. Both the trigger and the alternative are explicit.

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