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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds genuinely new behavioral context beyond that: the tool is free, prices are denominated in USDC on Base, settlement is via x402, and a payTo address is returned. It stops short of describing the response shape or caching/refresh behavior.

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 line beginning with 'Free:' puts the most decision-relevant fact first with no filler. It is a sentence fragment rather than a sentence, which slightly softens clarity, but nothing is wasted.

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 zero-parameter, read-only tool with strong annotations and no output schema, the description covers what the agent needs: cost of access, the currency/chain of the quoted prices, and the returned fields. Only the response format and the distinction from get_price are left unstated.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate beyond what the empty schema already conveys. The listed contents (prices, network, payTo) are effectively return-value information, which is useful but not parameter semantics.

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 names the exact resource and its payload: current per-call prices, network, and payTo address, including the settlement rail (USDC on Base via x402). It is clear what you get, but it never distinguishes itself from the similarly named sibling 'get_price', which risks confusion between pricing metadata and an asset price.

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?

Usage is only implied: labeling it 'Free' suggests it is the tool to call to learn what a paid call costs before spending, but there is no explicit when-to-use statement, no prerequisites, and no reference to alternatives such as get_price. An agent can infer the intent but gets no routing guidance.

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