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

Annotations already establish readOnly, idempotent, open-world, and non-destructive behavior. The description adds useful context beyond annotations: the tool performs live source fetching or web search, returns no verdict, makes no jury calls, and requires no payment.

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?

The description is a single front-loaded sentence that leads with 'Free preview' and efficiently covers the workflow, source handling, and explicit exclusions. Every clause contributes useful differentiation or behavior.

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 complex multi-step preview tool with no output schema, the description does well by explaining the pipeline and clarifying that no verdict is returned. It still leaves the response shape somewhat unspecified, though the 'show exactly what a paid fact_check_claim would check' phrasing provides reasonable expectation.

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%, so both the claim and sources parameters are already well documented. The description mentions live fetching/searching, which loosely reinforces the sources parameter fallback, but adds no syntax or constraints beyond 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 states a specific verb and resource: it decomposes a claim, fetches/classifies sources, groups them into independent families, and previews what a paid check would verify. It explicitly contrasts itself with fact_check_claim by saying 'No verdict, no jury calls, no payment,' so an agent can distinguish it from the paid sibling.

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 clearly frames this as a free preview of what fact_check_claim would check, which gives strong usage context. However, it does not explicitly state when to choose this over fact_check_status, fact_check_receipt, or fact_check_methodology, nor when not to use it.

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