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

Annotations (readOnlyHint, openWorldHint, idempotentHint) already establish safety, but the description adds substantial behavior: the two-path execution (structured vs grounded), the return of a verdict enum with specific meanings, the crucial distinction between 'could_not_verify' (check did not happen) and 'unsupported' (no source coverage), and the pipeworx:// citation format. This goes well beyond the annotations.

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?

Long but every sentence earns its place. Trigger phrases are front-loaded for quick scanning, the two execution paths are clearly separated, and the callout about could_not_verify vs unsupported is a necessary caveat. No redundant or filler content.

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 value semantics: the six possible verdicts, the actual value with citation, and reasoning. It also explains edge cases (could_not_verify, unsupported) and the tool's internal routing logic. This is complete for a tool of this complexity.

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 baseline is 3. The description enhances parameter meaning by explaining tolerance_pct's role: 'Overrides the tolerance implied by the claim wording — set 1–2 for hallucination detection where any material error must be refuted. Default: implied by wording, capped at 5.' This adds actionable guidance beyond the schema's plain description.

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 trigger phrases ('Is it true that…', 'fact check', 'verify the claim that…') and a clear verb+resource: natural-language claim verification against authoritative sources. It sharply distinguishes from sibling tools by explicitly scoping to factual correctness checks and by noting it replaces 4–6 sequential calls (NL parsing → entity resolution → data lookup → comparison).

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 provides routing guidance: company-financial claims take the SEC EDGAR + XBRL fast path, anything else falls through to the grounded pipeline. The 'Replaces 4–6 sequential calls' line gives a clear alternative, making when-to-use unambiguous.

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