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

With no annotations provided, the description carries the behavioral burden. It discloses the return shape (verdict, confidence, supporting/contradicting sources with URLs and stance) and a key behavioral trait: returning 'inconclusive' rather than a guess when evidence is unclear. This adds meaningful behavioral context beyond a simple 'check' label.

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 compact and front-loaded: the core purpose comes first, followed by output details and the valuable 'inconclusive' behavior. The sample endpoint and content-kit references are useful orientation, though the last sentence is slightly tangential to invoking the tool correctly.

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 simple one-parameter tool with no annotations and no output schema, the description is largely complete: it explains what the tool does, what it returns, how it handles uncertainty, and even provides a sample endpoint. It could add more detail on confidence-level semantics or source selection, but an agent has enough to call it correctly.

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% and there is one required 'claim' parameter, so the description must compensate. The phrase 'Check a claim against live web sources' makes it clear that the claim parameter is the statement to verify, which adds meaning beyond the bare schema type. It does not specify format or length limits, but for a single string parameter this is a minor gap.

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 names a specific verb and resource: 'Check a claim against live web sources' and specifies the exact output (verdict, confidence, sources with URL and stance). This clearly distinguishes fact_check from sibling tools like search, read_web_page, and summarize, which serve different purposes.

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 context is clear: use this tool when you have a specific factual claim to verify against live web sources, and the tool is designed to avoid guessing by returning 'inconclusive'. It does not explicitly name alternative tools or exclusion conditions, but the use case is unambiguous enough for an agent to select it correctly.

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