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

Annotations already mark readOnly/idempotent/non-destructive, and the description adds the crucial semantic distinction between could_not_verify, unsupported, and actual verdicts, plus the verification_error structure. It also discloses the routing behavior (financial vs non-financial) and the 'exact percent-delta math' for financial claims, which is beyond annotation info.

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 long but well-structured, with trigger phrases leading to capability, then routing details, then return semantics, then an 'IMPORTANT for callers' block. Every section adds necessary information for correct invocation and interpretation, though it could be tightened by removing some redundancy (e.g., listing both 'Is it true…' and 'true or false').

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 specifies the return value: the six verdict values, the actual value with citation, and reasoning. It also explains the two edge-case verdicts and that the tool replaces multiple sequential steps, giving the agent enough context to invoke it correctly and interpret results.

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 adds meaningful guidance for tolerance_pct: 'set 1–2 for hallucination detection' and explains the default is 'implied by wording, capped at 5.' The claim parameter is already well described with examples in the schema, and the description reinforces it with phrasing cues.

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 opens with concrete natural-language phrasings ('fact check', 'confirm or refute'), then states the resource: 'natural-language claim verification against authoritative sources.' It distinguishes itself from sibling tools by noting it replaces a 4–6 call pipeline and by specifying dual routing (SEC EDGAR vs grounded pipeline).

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?

Explicitly says 'Use whenever the agent needs to check whether something a user said is factually correct.' It also clarifies when not to interpret results as evidence: could_not_verify means the check didn't happen, and unsupported means no source exists. This gives clear decision guidance.

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