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

Annotations only declare readOnly/openWorld/idempotent; the description adds substantial context beyond them — the free-tier cap of top 3 results, the exact ranking signals (relevance, 30-day unique payers and calls, recency, price), and what the paid tiers unlock. An agent can predict both cost tier and ranking behavior before calling.

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 motivating question and the core behavior, then compresses return values and paid-tier upsell into tight clauses. The parenthetical list of paid routes is slightly promotional, but it earns its place by telling the agent where to go for deeper results.

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 still specifies return contents (match count, host count, top 3 services with name, USD price, networks, payers) and the limits of the free preview. An agent has everything needed to decide to call it and to interpret the response.

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 'need', 'network', and 'max_price' are already fully documented in the schema with an example and the enumerations. The description only restates that max_price and network are optional filters without adding semantics such as how 'need' matching works or how ties are broken. Baseline 3 is appropriate when the schema carries the load.

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?

Names a specific verb (searches) and resource (36,000+ paid x402 resources across public discovery indexes) and frames the user question it answers. It also states exactly what comes back — match counts, seller-host counts, and a top-3 ranked list with named fields — so an agent knows the shape of the result without opening a 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?

The opening question plus 'Free preview tier' establishes when to call this, and the final sentence enumerates the paid routes (/v1/lite, /v1/pick, /v1/market) that supersede it for resource URLs, live 402 checks, or market reports. That is a clear escalation path, though no explicit 'do not use for X' exclusion is stated and there are no siblings to contrast against.

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