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

Adds major context beyond annotations: exact price ($0.25 USDC, amount 250000, Base), the required PAYMENT-SIGNATURE header, the HTTP 402 challenge shape, and the safety property that a misconfigured jury fails before payment is requested. It also discloses the coherence formula and anti-hallucination substring gate, consistent with the openWorldHint/non-idempotent 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?

Front-loads the two most decision-relevant facts (paid tool, cost) and packs a lot of genuinely useful information. The core sentence is an extremely long run-on with nested clauses, which slightly hurts scannability, but no sentence is filler.

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 does the work of explaining the return surface: per-source entailment with verbatim-quote evidence, a coherence-gated verdict, and a stored receipt. That is nearly complete; only a concrete response shape (field names/structure) is left implicit.

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 claim, sources, and sub_claims are already fully documented in the schema. The description mentions decomposition behavior but adds no syntax, format, or constraint detail beyond what the schema provides, so the baseline 3 applies.

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?

States a specific verb+resource ('fact-check a claim against live web sources') and even summarizes the internal pipeline (decomposition, per-source entailment, coherence-gated verdict). However, it never names or distinguishes itself from the four siblings (fact_check_preview, fact_check_status, fact_check_receipt, fact_check_methodology), so an agent gets no routing signal.

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?

Gives useful conditions about payment ('send the x402 PAYMENT-SIGNATURE header', 'without payment the call returns the canonical x402 challenge') and the jury-unconfigured failure path. But it offers no guidance on when to use this paid end-to-end tool versus the free preview or the receipt/status siblings, which is the main selection decision an agent faces.

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