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

With no annotations, the description carries the disclosure burden well: it states the exact output composition and, unusually, the cost model ($0.01 USDC per call, paid via x402 on Base). It does not mention rate limits or failure behavior, but the payment and return contents are the key behaviors an agent needs.

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 with no filler; the resource and return shape are front-loaded, and the pricing note is appended as secondary context. Minor density makes it read as a list but 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?

For a single-parameter tool with no output schema, the description fully explains return fields (tenor, yield %, as-of date, source, changes) and the payment requirement, leaving an agent equipped to call it. Only rate-limit/error handling is absent, which is minor here.

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% and the single country parameter is fully documented in the schema with the same US/EA/MA values restated in the description. The description adds no syntax or format detail beyond the schema, so baseline 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?

States a specific resource ('Full government yield curve') and the exact return shape (tenor -> yield %, as-of date, source, changes). The word 'full' implies differentiation from the single-value yields_rate sibling, but it never names an alternative explicitly.

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 word 'full' subtly implies this is the complete-curve option versus a single rate, and the country list scopes it, but there is no explicit when-to-use/when-not guidance or naming of alternatives like yields_rate or yields_spreads.

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