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

The readOnlyHint annotation already tells the agent the call itself mutates nothing, and the description goes well beyond it by disclosing the $0.01 USDC cost, the Solana mainnet payment requirement, and the required retry sequence. It stops short of covering failure modes such as challenge expiry or whether a signature can be reused.

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: the first front-loads what the tool returns and its price, the second explains the call sequence. No filler and no redundancy.

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?

With no output schema, the description still conveys what comes back conceptually (price plus source proof) and what the first unpaid call yields (a payment challenge). It omits error handling and the exact shape of the challenge/paid responses, which is a modest gap for a paid endpoint.

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%, so both id and payment_signature are already fully documented in the schema, including the omit-then-resend semantics. The description restates that flow in prose without adding format, validation or edge-case detail beyond the 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+resource: a point-in-time asset price with source proof, plus its cost. It is clearly distinct from sibling tools like get_peg, get_metric or get_brief, though it never names an alternative to route the agent explicitly.

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 clear, actionable context for the two-call payment protocol: omit payment_signature first to get the challenge, pay, then call again with the signature. It does not, however, compare itself against any sibling tool or say when a different price/peg tool would be preferable.

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