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

Annotations cover readOnly and openWorld, and the description adds real behavioral detail: the four outcome statuses, per-claim results with passage/offset/hash/fetch time, plus concrete constraints (20 claims paid / 3 free, public http(s) only, 2 MB per page). The free-tier limit wording is slightly ambiguous about which tier applies, keeping it from a 5.

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?

Three dense sentences: action, return shape, motivation, then constraints. Front-loaded with the core operation and no filler.

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 fully covers return structure (statuses, source passage, character offset, HTTP status, content hash, fetch time) as well as quotas and scope limits. An agent has everything needed to call and interpret it.

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 0%, but the single param is a self-explanatory claims array of {id, url, quote}, and the description reinforces the quote/url pairing and adds the meaningful per-call claim limit. The role of the optional id field is left unstated.

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 — fetches each cited URL and checks whether quoted text appears — and is unmistakable against siblings like validate_json or csv_quality. An agent knows exactly what operation this performs.

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?

"Catches hallucinated or drifted citations before an agent relies on them" gives a clear trigger condition, and the quoted-text framing implies it is for citation claims, not general URL checking. It stops short of naming when-not or an explicit alternative tool.

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