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

With no annotations, the description carries the full behavioral burden. It usefully discloses the price ($0.003 USDC per call via x402 on Base) and the return shape (tenor -> yield %, as-of date, source, change in bp), but it does not mention rate limits, failure modes, or any other operational constraints.

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 tightly written sentences: the first front-loads the core data description and return fields, and the second cleanly states the payment model. No wasted words, and the most important information comes first.

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, read-only data tool with no output schema, the description supplies the essential return-value context (tenor/yield, as-of date, source, changes in bp) and the pricing model. It is nearly complete, though it could clarify whether only the latest curve is available or whether as-of dates can be requested.

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?

The single country parameter is already fully documented in the schema at 100% coverage, including the US/EA/MA options. The description repeats the same country list without adding syntax, format, or edge-case details beyond the schema, so the baseline of 3 applies.

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 states a specific resource (full government yield curve) and the exact country coverage (US, EA, MA), so the agent can tell what data it returns. However, it does not explicitly differentiate this tool from siblings like yields_rate or yields_spreads, leaving the agent to infer the distinction.

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?

There is no explicit when-to-use guidance or comparison to alternatives. The description says what data is available but does not tell the agent when to choose yields_curve over yields_rate or yields_spreads, nor does it mention any prerequisites or exclusions.

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