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

With no annotations, the description carries the full burden and does well on the operational side: it discloses a $0.01 per-call cost via x402 (USDC on Base), that omitting payment yields a free quote, and that responses carry a provenance chain and Ed25519 attestation. It stops short of defining the rolling-window length, data freshness/lag, or rate limits.

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?

Two tight sentences with zero filler: purpose first, then cost and response properties. Front-loading is correct and every clause carries information, though the split of commercial details into a second sentence is slightly dense.

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 no-annotation, no-output-schema metric tool, the description covers the output properties (provenance, attestation) and the commercial model, which is above average. However, it leaves the unit of analysis underspecified — 'rolling window' is never quantified, and the shape of the returned counts (single value vs. series) is not stated, which an agent needs to call it correctly.

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% for the single 'payment' parameter, which the schema itself documents in detail (legacy base64 header, prefer _meta["x402/payment"], omit for free quote). The description adds nothing about the parameter beyond restating the pay-per-call model, 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+measure: newly incorporated UK companies counted per day, sourced from Companies House advanced search. It is clearly distinguishable in substance from the similarly-named sibling uk_company_lookup (aggregate daily count vs. single-company lookup), though it never names that sibling explicitly.

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?

There is no when-to-use guidance and no alternatives. The closest sibling, uk_company_lookup, is never mentioned, so an agent must infer from the name alone whether it wants a daily count or a company detail lookup. The only usage signal is the implicit 'per day' time-series framing.

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