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

No annotations are provided, so the description carries the full burden of behavioral disclosure, and it delivers: it discloses that the free tier returns unsigned, rate-limited results, that the paid tier yields a signed attestation with no daily limit, and that output is a signed 0-100 trust score with evidence URLs. It also surfaces the payment-header mechanism and transport equivalence. It could add failure semantics for unverifiable domains, but the disclosure is unusually thorough for a tool with zero annotation support.

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 purpose is front-loaded in the first sentence, which is excellent, but the description runs long with dense commercial detail — batch pricing thresholds, x402 header format variants (PAYMENT-SIGNATURE v2 vs X-PAYMENT v1), USDC amounts, and transport equivalence. Much of this is actionable for invocation but is more than an agent needs to decide whether to call the tool, and some is inessential overhead for selection.

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 tool of moderate complexity with a trivial one-parameter schema and no output schema, the description is unusually complete: it covers invocation, return shape (signed attestation, trust score 0-100, evidence URLs), free vs paid auth paths, rate-limit behavior, and the batch alternative. The only gap relative to siblings is the absence of explicit disambiguation against verify_claim/verify_freshness/verify_price, but nothing an agent needs to call it correctly is 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% and there is only one parameter (domain), which the schema already documents clearly with an example. The description adds behavioral context about what happens to the domain (RDAP, DNS, SPF/DMARC, HTTPS checks) but no additional format or constraint details beyond the schema's 'example.com'. With full coverage, baseline 3 is appropriate.

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 a specific verb and resource ('Verify a business or domain is real and established') plus concrete trigger scenarios ('pays an invoice, onboards a vendor, or trusts it'). The verification methods are enumerated (RDAP age, DNS, email posture, HTTPS), which clearly distinguishes it from siblings like verify_claim, verify_freshness, and verify_price — those are all different verification facets, so an agent can tell this apart without opening any schema.

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?

It states when to use the tool (before paying invoices, vendor onboarding, fraud/KYB checks) and explicitly routes multi-domain workloads to the batch endpoint with a cost comparison ('cheaper from four domains up'). It also delineates free vs paid tiers by signing and rate-limit needs. It lacks an explicit 'use verify_claim instead when...' exclusion against its siblings, but the use-case context is strong enough to guide selection.

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