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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered; the description adds genuinely new behavior: the tool only returns the unpaid 402 and never pays, plus the price and payment rail (USDC on Base). The legal disclaimers about New York Fed affiliation and investment advice add little operational value for an agent.

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?

The critical constraint (returns an unpaid 402, never pays) and the payment URL are front-loaded in the first two sentences. The remainder is product and legal boilerplate, but for a paid-quote tool that context is relevant and does not bury the operational instruction.

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 one-parameter quote tool with no output schema and full annotation coverage, the description covers what is returned (a 402 quote rather than the report), what the report contains, and how payment is completed. An agent has enough to call it correctly and act on the result.

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 a single parameter at 100% schema description coverage, the schema already documents 'id' as coming from funding_reports or defaulting to latest. The description only echoes 'by id or latest' and adds no syntax, format, or failure-mode detail beyond that.

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 opening sentence gives a precise verb and resource: it returns payment instructions (an unpaid HTTP 402 quote) for a single $1 report, and explicitly states it never pays. This distinguishes it from an actual payment step and from the sibling listing tool funding_reports referenced in the schema, though it never names funding_reports or x402_check directly as alternatives.

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?

It clearly tells the agent the next step: pay the 402 over HTTP with x402 v2 (USDC on Base) at the given GET URL, implying this is a quote-only step before external payment. It also points to an alternative resource for a different need (raw published values are free at /api/money-market-rates), but it does not explicitly state when to prefer x402_check, x402_check_deep, or funding_reports over this tool.

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