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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. Beyond that, the description adds two genuinely new behavioral facts: a 2-credit cost and that curve spreads, inversion flags, curve shape, and breakeven inflation are gated behind paid plans. It does not describe rate limits, data latency, or update cadence.

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 the core capability and followed by the tier/cost caveat. Minor waste in the opening 'Treasury Yields: Treasury Yields provides' repetition of the title, and a slightly promotional tone around paid-plan features.

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?

This is a simple zero-required-parameter read tool with an output schema, so return-value explanation is unnecessary. The description covers data scope, historical depth context, feature tiering, and cost, which is everything an agent needs to call it correctly.

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 both optional parameters are fully documented in the schema with formats, examples, and defaults. The description only restates the available maturity span ('1-month through 30-year') and TIPS coverage, which reinforces but does not substantially extend the schema's meaning.

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 verb and resource: it retrieves current and historical US Treasury constant-maturity yields across 1-month to 30-year maturities plus TIPS real yields. Scope is precise enough that an agent knows exactly what data comes back, though it never distinguishes itself from adjacent rate tools such as InterestRate, BenchmarkRate, or I-BondRates.

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 and no named alternative. The only decision-relevant signal is the '(Cost: 2 credits)' note and the mention that some features require paid plans; the agent is left to infer when Treasury curve data is preferable to other interest-rate siblings.

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