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

Beyond the readOnlyHint annotation, the description discloses the truly non-obvious behavior: this is a paid endpoint ($0.05 USDC per call) using a challenge/response protocol on Solana mainnet. That is a substantial addition. It stops short of covering failure modes, signature reuse, or timing, keeping it out of the top band.

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 dense sentences, front-loaded with what the tool returns and its cost, followed by the exact call sequence. Every clause carries load; 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?

With no output schema, the description's 'with source proof' gives a useful hint at return content, and the payment protocol is fully explained. It is nearly complete, missing only return-format detail and error handling for a paid call.

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 already documents both id (with examples) and payment_signature in detail, so the schema carries the burden. The description only reinforces the payment step ('pay the exact USDC on Solana') without adding new parameter semantics, matching the baseline 3.

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 ('Point-in-time asset price') plus a distinguishing quality ('with source proof'), so the agent knows what it retrieves. It does not, however, contrast itself with near-siblings like get_peg or get_metric, leaving that differentiation implicit.

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 lays out the operational two-call flow (first call gets a challenge, pay, then call with payment_signature), which is genuine usage guidance. But it never states when to prefer this over get_metric/get_peg or any exclusion conditions, so routing among siblings is left to inference.

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