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

Discloses a pay-per-call cost ($0.05 USDC), the settlement network (Solana mainnet), and the challenge/response handshake — none of which the readOnlyHint annotation conveys. It stops short of stating failure modes, whether the challenge expires, or how payment is verified, so it is not a full 5.

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?

Two tight sentences, front-loaded with purpose and price, followed by the exact call sequence. Every clause carries information an agent needs to invoke it successfully.

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 two-parameter read tool with no output schema, the description covers cost, payment mechanics, and sequencing. It leaves open what a successful response looks like and what errors occur on unpaid or invalid signatures, which is a modest gap.

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 description coverage is 100%, and the schema itself already explains the payment_signature challenge flow and lists example metric names. The description largely restates that flow, adding only the price figure, so baseline 3 is appropriate.

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 ('Get one verified stablecoin/RWA market metric') with a concrete cost attached. It does not, however, differentiate itself from siblings like get_price or get_peg, which an agent would have to infer from their own definitions.

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?

Gives an explicit two-step invocation protocol: call without payment_signature to receive the challenge, pay, then call again with the signature. That is real when/how guidance, but it offers no guidance on choosing this tool over get_price/get_peg/get_brief.

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