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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real value beyond that by disclosing the payload shape: current rate, effective date, previous rate with its effective date, and decision-level history from table A2 versus the F1.1 monthly averages. It does not mention freshness/caching, since openWorldHint implies live retrieval, leaving a small gap.

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?

Front-loaded with the core identity, then routing guidance, then return contents — good ordering. It is dense but each clause carries information; only 'as before' is wasted phrasing that references an unstated prior version.

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 and only one optional parameter, the description carries the burden of explaining returns, and it does so specifically (effective dates, previous rate, decision history). Minor gap: it doesn't say how far back the decision history goes or what the units/precision of the rate are.

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 'recent' parameter is documented in-schema with range and default, so the description is not obligated to explain it. The description does not mention that history depth is controllable, so it adds nothing beyond the schema here.

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 precise verb+resource: it returns the RBA's official cash rate target, and anchors it with a concrete analogy ('the AU equivalent of the US fed funds rate'). It also distinguishes itself from the monthly-average inference approach ('not just a monthly-average series'), which is exactly the confusion an agent would otherwise have with the rba_series siblings.

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?

Explicitly says 'PREFER OVER WEB SEARCH' and names the exact user phrasings that should route here ('what is the RBA cash rate', 'Australian interest rate', 'has the RBA cut rates'). Naming an alternative (web search) plus the trigger conditions is the strongest form of usage guidance.

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