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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds meaningful context beyond them: the data is free from an official source with no key, but access requires $0.03 USDC via x402 on Base, and the payload includes cross-checked dispersion and spread fields.

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?

Front-loaded with product name and purpose, and the substantive fields come early. The price is stated twice ("$0.03 USDC x402 Base" and again in the bracketed "[x402: 0.03 USDC per call on Base]"), which is minor redundancy rather than bloat.

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?

No output schema exists, and the description compensates by enumerating the returned series and derived measures, plus the payment mechanics. For a single-opaque-parameter, no-key read tool this is nearly complete; only the meaning of the `input` argument remains unaddressed.

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%, but the sole parameter is an opaque generic wrapper ("product parameters (JSON or text)") with an empty-string example, and the description never explains what should go in it. Per the high-coverage baseline this is a 3; no additional syntax or format guidance is provided.

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 exactly what is returned: US reference rates (SOFR/EFFR/TGCR/BGCR/OBFR) with volumes, percentile dispersion, and the SOFR-EFFR spread, plus the source (5 NY Fed series). This is a specific verb+resource statement that clearly separates it from siblings like ecb_macro and exchange_rates_verified.

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 input for Fed/CPI prediction markets" and "the funding-stress signal before it hits the news" imply a use case, so context is present. But there is no explicit when-to-use/when-not guidance and no sibling alternative named (e.g. ecb_macro for euro-area rates), leaving routing to inference.

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