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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so safety and determinism are covered. The description adds genuinely useful behavioral context beyond that: the units (percent per year), the as-of date accompanying the values, and the data source (Propely), which tell the agent how to interpret and cite the result. It still does not state update frequency or whether a single snapshot vs. history is returned.

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?

Three sentences, front-loaded with the actual returned data and followed by units and source. The home-loan pricing sentence is mildly tangential to invocation but does help the agent judge relevance; the attribution sentence is short and harmless.

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 the return, and it does so adequately: which two tenors, the unit, and the as-of date. The main residual gap is freshness/update cadence and whether historical values are available, but nothing essential to calling a zero-argument tool is missing.

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?

The tool takes zero parameters, which is the baseline-4 case; there is nothing for the schema to document and nothing for the description to compensate for.

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 precise resource (1-month and 3-month compounded SORA for Singapore), the units (percent per year), and the accompanying as-of date, so an agent knows exactly what it fetches. It implicitly separates itself from the sibling calculators (TDSR, BSD, ABSD) by being a pure rate lookup, though it never explicitly contrasts itself with them.

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 only implied: the note that Singapore floating-rate home loans are priced as SORA plus a bank spread hints at why an agent would want the rate, but there is no explicit when-to-use, when-not-to-use, or reference to any sibling tool such as calculate_tdsr.

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