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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuine behavioral context beyond that: it returns a heuristic coverage score and prioritized fixes, and it discloses a cost ($0.01 USDC via x402), which is a material payment prerequisite for invocation.

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?

Three tight sentences, front-loaded with what it audits, followed by output nature and exclusions, and closing with cost. Every sentence carries distinct, non-redundant information.

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?

An output schema exists, so return values need no explanation, and the description still summarizes the shape of the return (heuristic score plus prioritized fixes). With a single fully-documented param, clear scope, exclusions, and pricing disclosed, an agent has everything needed to decide and call 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?

There is a single parameter with 100% schema description coverage, and the schema fully documents that domain must be a public domain without scheme, path, or port. The description adds no format or syntax detail beyond the schema, so the baseline of 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 (audit) and resource (store) and enumerates exactly what is checked: machine-readable product metadata, UCP/ACP discovery, payment hints, and robots.txt access. An agent can distinguish this from siblings like pre_purchase_merchant_trust_check or universal_product_url_to_json 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?

The 'Use to audit...' phrasing gives clear context for invocation, and the explicit exclusion ('Not Meta certification or a live checkout test') tells the agent when this is not the right tool. It stops short of naming a specific sibling to use instead, so it is strong context rather than full routing.

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