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 genuinely useful behavior beyond that: a per-call cost of $0.002 in USDC via x402 on specific chains, and that failed calls are not charged — meaningful cost/authorization disclosure. It does not describe response shape or ordering guarantees beyond 'newest first', so it sits at a solid middle score rather than the top.

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 sentences, front-loaded with what the tool returns, then scope, then cost — logical ordering with little waste. The pricing clause is dense but each piece (cost, currency, payment rails, failure policy) is actionable, so it earns its place.

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?

The tool is simple (one optional parameter, output schema present), so return values need no explanation. The description covers scope, pagination limits, and cost/auth requirements, which is close to complete; the only gap is guidance on when this feed is preferable to sibling store feeds.

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 the single `limit` parameter already documents its range and default, so the schema does the heavy lifting. The description adds a small amount of meaning by explaining that only the first page is read, which contextualizes the effective cap on `limit`, though it does not restate the range itself. Baseline 4 is appropriate when the schema fully documents the only parameter and the description reinforces rather than duplicates it.

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 states a specific resource (fabrics on Mood Fabrics' public product feed) and enumerates the fields returned (title, type, variant prices, stock status). It differentiates from the many sibling store feeds largely by naming the retailer, which is adequate but not an explicit contrast with alternatives.

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 clarifies the data scope ('only the feed's first page is read, newest products first') and states the payment prerequisite, which are useful usage constraints. However, it gives no explicit guidance on when to pick this tool over the dozens of other ecommerce_* feed tools, leaving selection to be inferred from the store name.

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