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

With no annotations at all, the description carries the full behavioral burden, and it does disclose meaningful traits: every row is date-stamped with the provenance of its figures, and hosts absent from the registry are reported as 'unknown' rather than fabricated. It leaves out data freshness/latency, cost, and what a failed lookup row actually looks like, which keeps it short of a 5.

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 sentences, no filler, and the core scope (2-5 hosts, side by side) is front-loaded before the field list. The first sentence is a long comma-run of dimensions, but each clause adds a distinct comparison axis and the final two sentences cover edge cases rather than padding.

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?

There is no output schema or annotations, so the description must stand in for return-shape information, and it does so by enumerating the compared fields and the unknown-host behavior. What is missing is minimal but real: effective host cap beyond the schema, and any notion of data freshness or retrieval latency.

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% and the single `hosts` parameter already documents the array with an example, so the baseline is 3. The description adds only marginal meaning by clarifying these are seller hosts the registry must list, but adds no format or validation detail beyond the schema.

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 concrete action ('two to five seller hosts side by side') plus an enumerated set of comparison dimensions (price range, x402 payments, payer wallets, concentration, operator group), so the resource and scope are unambiguous and clearly multi-host. It never names a sibling tool, so the contrast with single-host tools like `seller` is only implied rather than stated.

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 2-5 host range implies this is the multi-host comparison path, and the schema enforces minItems/maxItems, so an agent can infer when to reach for it. However, there is no explicit when-to-use versus `seller`, `search`, or `operator`, and no exclusions or prerequisites are given.

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