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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description goes beyond this by explaining that historical rates come from the SAME contract, that the two strips are fundamentally different rate benchmarks, and that results are percentages. This prevents real misinterpretation and adds value beyond annotations.

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?

The description leads with the core answer—'What the market is paying for US interest rates'—and each sentence contributes useful either interpretative or structural detail. It is a bit dense, especially the strip-composition details, but no sentence is pure filler.

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?

With no output schema, the description carries the burden of explaining return content, and it does so by stating each contract's current and historical rates. It covers the important pitfalls—percent units, traded-versus-forecast status, lane comparability—and is generally complete for a read-only data tool, though it does not explicitly describe how the `history` parameter changes the returned shape.

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 both parameters are already documented. The description adds practical meaning by elaborating the lane values (16 quarterly SOFR contracts vs 48 monthly fed funds contracts) and framing history as same-contract rates six and twelve months ago. This gives the boolean `history` parameter concrete semantics.

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 identifies a specific resource: US interest-rate futures strips out to four years, with two lanes (`sr3` and `ff`) and their contract structures. It does not use an explicit action verb like 'get' or contrast itself against a sibling tool, so it does not fully reach the top of the scale, but the resource and scope are clear.

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 description gives strong within-tool usage guidance: these are traded prices, not forecasts, and the two lanes should not be compared contract by contract. However, it does not state when to prefer this tool over nearby siblings such as get_rates_and_curve or get_treasury_curve, so the choice-when-to-use case is only implied.

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