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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive. The description adds meaningful behavioral context beyond that: no wallet, no payment, no arguments, and a sample response rather than real-time data. It stops short of saying whether the sample is static or how it is produced, but this is a useful addition.

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?

A single, front-loaded sentence that leads with [FREE] and then explains the preview purpose and its zero-argument, no-payment nature. No wasted words.

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?

For a no-parameter, no-output-schema preview tool, the description covers the essential agent needs: it is free, safe, requires no inputs, and exists to show the response shape. It could say more about what fields the sample contains, but calling it inherently reveals that shape.

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?

With zero parameters, the baseline is 4 per the rubric. The description reinforces this by explicitly stating 'no arguments needed,' which aligns with the empty input 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?

States a specific verb and resource: it returns a free sample response for token_price (Base token price via Chainlink/Uniswap), letting the caller preview the shape. It clearly distinguishes itself from its paid sibling token_price by labeling itself [FREE] and mentioning the 0.003 USDC cost of the real 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 gives a clear usage context — use this to see the response shape before paying for token_price — and names the paid alternative it precedes. It does not explicitly state 'use token_price for live data,' but the preview-before-payment framing makes the routing unambiguous.

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