Actuarial present value

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, but the description adds behavioral context beyond them: it specifies error semantics (unknown method, missing input, or extra field returns an INVALID_ARGUMENT error envelope instead of raising), the no-defaults rule, and the IFRS/HKFRS scope restriction. This is meaningful disclosure 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?

Front-loads purpose, then usage/exclusion, then method input lists, and closes with error behavior. Every sentence carries required information (frameworks, alternative tool, per-method inputs, error contract) with no filler, which is appropriate density for a 5-method, 14-parameter tool.

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?

An output schema exists, so return values need not be explained. The description covers scope, method selection, required inputs per method, and error behavior, leaving nothing an agent needs in order to invoke this tool correctly.

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; however, the description adds the critical method-to-input mapping that the schema's method.enum explicitly defers to (e.g., ifrs17_gmm needs cash_flows, discount_rate, risk_adjustment; ias19_puc needs projected_benefits, discount_rate, attribution_years). Without this mapping the 14 flat parameters would be unusable, so the description materially compensates.

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+resource ('Actuarial present value engine', 'Discount expected cash flows with mortality, survival, and risk adjustment') and names the regulatory frameworks (IFRS 17, IAS 19, IFRS 2, IAS 37). It explicitly distinguishes itself from the sibling calculate_expected_value by excluding generic probability weighting, so an agent can tell the two apart without opening a 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 states when to use ('for regulated IFRS/HKFRS obligations only'), when not to use ('does NOT do generic project or scenario probability weighting'), and names the alternative tool (calculate_expected_value). It also defines the invocation rule ('Supply exactly one method with its declared inputs (no defaults)') that governs correct use.

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