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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds materially new behavioral facts: a $0.01 USDC charge per successful call via x402 on Solana, the equivalent HTTPS endpoint, and the as-of semantics that resolve to the latest published date on or before the requested one. The payment requirement in particular is critical context no annotation conveys.

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?

One dense but front-loaded paragraph: what the data is first, then default/as-of behavior, then price and the alternative transport. Every clause carries information, though the single unbroken sentence is harder to scan than a short bulleted structure would be.

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?

There is no output schema, and the description compensates by enumerating the returned fields (par curve 1M-30Y, bp day-over-day change, 2s10s, inversion flag, TIPS curve, total debt / public debt / intragovernmental holdings). Combined with pricing and transport details, an agent has everything needed to call and interpret results.

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 coverage is 100%, so the baseline is 3, but the description adds meaning beyond the schema by explaining that the 'real' curve means TIPS real yields and that 'debt' toggles the Debt to the Penny block with its three components. Defaults (latest, debt=true) are restated in the schema, so the marginal gain is modest but real.

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 description names a specific resource (US Treasury par yield curve + Debt to the Penny), enumerates the tenors and derived metrics (2s10s spread, 3m10y inversion flag), and cites the upstream sources. It does not distinguish itself from closely related siblings like us_macro, macro_indicators, or fx_rate, so an agent gets a clear picture of the tool but no explicit differentiation.

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?

"Latest by default or as of a past date" gives clear operational guidance for the date parameter, and the pricing line sets expectations for cost. However, there is no explicit statement of when to choose this over macro_indicators/us_macro, nor any exclusions about what data it does not cover.

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