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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the pay-per-call x402 USDC on Base payment model and the fact that a payment challenge is returned when payment is missing, which an agent must know to handle the response correctly.

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 sentences, front-loaded with what the tool returns and followed by the payment caveat. Every clause earns its place; nothing is padded or repeated.

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?

An output schema exists, so return values need no explanation, and the payment behavior is disclosed. The one gap is that the history-window parameter is never acknowledged in prose, but the schema covers it, leaving the definition largely complete for a simple read tool.

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% and the single 'months' parameter is fully documented in the schema with its default, so the schema carries the semantics. The description adds no parameter detail, making the baseline 3 appropriate.

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 the specific resource (US Treasury rates) and the scope of coverage (bills, notes, bonds, TIPS), which is enough for an agent to distinguish it from generic siblings like yields or macro. It does not explicitly contrast itself with the closest sibling, yields, but the 'official US Treasury by security type' framing is specific and non-tautological.

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?

Usage is implied rather than stated: an agent can infer this is the tool for official Treasury curve data, and the description notes the security types available. However, it gives no explicit when-to-use versus alternatives (e.g. yields), no conditions, and no exclusions.

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