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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering safety and idempotency. The description adds 'FREE' (cost to call) and clarifies the return content (prices and settlement rails), which annotations do not cover. It does not contradict annotations, and the added context is useful for an agent deciding whether to invoke it.

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?

The description is a single, efficient sentence that front-loads the key benefit ('FREE') and states the exact content of the catalog. Every word adds value, with no redundancy or filler. The structure is ideal for quick agent scanning.

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 (zero parameters, no output schema), and the description sufficiently conveys what the caller will receive: a catalog of all paid resources with USD prices and settlement rails. While it does not specify the exact response format (e.g., JSON array), the description is adequate for an agent to know what to expect and how to use the data. No critical information is missing for a tool of this complexity.

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 are zero parameters, so the schema is trivially documented at 100% coverage. The description correctly adds no parameter-specific detail because none exists. Per rubric, a baseline of 4 applies for zero-parameter tools, and the description does not need to compensate for any schema gaps.

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 clearly states a specific resource ('every paid resource'), its attributes (USD price and settlement rails), and positions it as a catalog. This distinguishes it from sibling tools like swap_evm_price or token_report, which serve different purposes. The 'FREE' prefix immediately signals the tool is safe to call.

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 description implies usage—consult this catalog to learn costs before calling paid tools—but it does not explicitly state when to use it versus alternatives or provide any exclusion criteria. There is no mention of when not to use it, but the zero-parameter design makes it self-evident for pricing lookups. A score of 3 reflects the lack of explicit guidance while acknowledging the implied context.

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