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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, and the description is fully consistent with a pure calculation tool. It adds genuinely useful context the annotations cannot: the ABSD rate assumptions (SC 20%->0%, PR 30%->5%), the 2.5% p.a. CPF interest assumption via yearsHeld, and the caveat that figures are indicative and not legal or financial advice.

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?

Purpose and comparison are front-loaded in the first sentence, followed by outputs, provider attribution and disclaimer. The provider line is mild promotional padding, but the disclaimer earns its place for a financial-estimate tool; overall it is appropriately sized.

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 returns, and it does so by naming BSD/legal costs, ABSD saved, CPF refund and break-even price. Assumptions and the indicative-figures caveat are also covered, leaving only minor gaps such as how the break-even price should be interpreted.

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%, so the baseline is 3, but the description adds meaning beyond the schema by explaining the consequence of the profile parameter (ABSD rates differ for sc vs pr) and tying cpfUsed/yearsHeld to the CPF refund calculation. It does not clarify edge cases such as partial shares or the sharePercent transfer mechanics, so it falls short of a 5.

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 verb and resource (estimate whether decoupling is worth it) and details exactly what is computed: BSD and legal costs versus ABSD saved, plus CPF refund and break-even price. This clearly separates it from siblings like calculate_absd and calculate_bsd, which compute single components rather than the decoupling trade-off.

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 scenario is scoped explicitly ('before buying another property'), giving a clear when-to-use context. It does not, however, name alternative tools (e.g. calculate_absd for a standalone ABSD figure) or state when this tool is the wrong choice, so it stops short of full routing guidance.

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