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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description earns credit for adding publishing cadence ('zero/forward fitted data publish monthly') and provenance details ('each point says whether it is observed or derived'). The freshness caveat is material for a data-retrieval tool and is not present in the 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 purpose is front-loaded in the opening clause and the two follow-up sentences add genuine constraints rather than filler. The first sentence is a dense multi-clause list, but it remains readable and every element carries information.

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 describing returned data, and it does so reasonably: yields, fitted curves, observed-vs-derived markers, source digest and convention. It stops short of describing the response shape or how multiple families interleave, but it is sufficient for correct invocation.

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 67%, and the schema already spells out date, compareDate and the family enum. The description only adds the count of families ('eight distinct cash/government families') without mapping individual enum values or explaining the family semantics, so it does not meaningfully compensate for the coverage gap. Baseline 3 is 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?

States a specific resource (RBA curve nodes) and enumerates the returned content: cash and bond yields as published plus fitted zero, forward and discount curves with observed/derived flags. It does not name a specific sibling to contrast against, but the scope is unambiguous enough to separate it from rate_history or compare_rates.

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?

Gives explicit selection context ('exact date or the latest publication') and an explicit exclusion boundary ('no intraday OIS, BBSW, swap or futures feed'). It does not name alternative sibling tools for those excluded use cases, so the routing stops just short of a 5.

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