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

Beyond the readOnly/openWorld annotations, the description discloses cost ($0.002 USDC per successful call), payment mechanism (x402 on Base/Solana/Arc), and the important billing behavior that failed calls are not charged. It also states the maximum entity count and return fields, adding substantial operational context.

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 definition is front-loaded with the core action and then layers scope, exclusions, return fields, and pricing without wasted text. Each clause contributes either selection guidance or operational transparency.

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 single-parameter lookup tool with full schema coverage, annotations, and an output schema, the description supplies the remaining decision-critical context: what it does, what it explicitly does not do, what it returns, and how billing works. Nothing essential for correct invocation appears missing.

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 statement parameter is already documented with its 10–1000 character range. The description adds useful semantic detail by explaining that the tool searches for up to three capitalised names or phrases and ignores numbers and dates, going beyond the schema's basic type/length 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 gives a specific verb and resource: it extracts up to three capitalised names/phrases from a statement and resolves each against Wikidata. It also explicitly distinguishes the output and scope, including the clarifying limit that it confirms entity existence rather than judging claim truth.

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 states clear when-not conditions: it does not judge whether a claim is true and does not find numbers or dates. It does not explicitly name alternative tools such as hallucination_claim_checker or web_search_turbo, so the routing guidance is strong but not fully comparative.

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