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

With no annotations, the description carries the full behavioral burden and does substantial work: it discloses the cost-matching method (equalizing true out-of-pocket cost), the fee/tax mechanics applied (entry/exit fees, AUM fees, first-year commission, exit tax), and flags that forecast returns and omitted fee/tax inputs are modelling assumptions rather than user facts. The explicit prohibition on inventing personal contribution amounts is valuable guardrail context. It stops short of describing result shape or horizon behavior, though an output schema exists.

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 comparison definition and followed by usage, prerequisites, and assumption warnings in a logical order. The second sentence ('Use to compare taxable investment with a tax-deductible investment vehicle') largely restates the first and could be merged, but no sentence is otherwise wasted.

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?

For a 14-parameter financial modelling tool with no annotations, the description covers required inputs, fee/tax mechanics, assumption policy, and the no-invention guardrail; return values are covered by the output schema. What remains thin is guidance on the many optional fee/tax parameters (e.g., when an omitted value is safe versus must be asked for), though the schema descriptions carry that detail.

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 baseline would be 3, but the description adds a genuinely non-obvious semantic: the two options are compared at matched out-of-pocket cost, which explains why only option 2's gross contribution is required. It also names the three required inputs, reinforcing which fields cannot be defaulted.

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: compares a taxable investment (option 1) against a tax-deductible vehicle such as a provident fund or life-insurance savings plan (option 2). The scope is narrow enough that an agent can distinguish it from neighbors like compare_rent_vs_buy or analyze_portfolio without opening the schema.

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 when to use it ('Use to compare taxable investment with a tax-deductible investment vehicle') and names the three inputs that must be present (annual contribution, tax-relief rate, option 2 management fee). It adds an operating rule — reuse supplied facts and ask only for missing essentials — but gives no when-not guidance or named alternative for cases outside this comparison.

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