finance.pv

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

Beyond the annotations (readOnly/idempotent/closed-world), it discloses that the calculation uses a fixed 50-digit precision independent of caller settings, that out-of-range results are treated as input errors, and that inputs must be finite. That is exactly the kind of behavioral context annotations cannot express.

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 purpose and formula, then constraints, then precision/error behavior — a sensible order with little waste. A couple of clauses slightly restate earlier constraints (finiteness, decimals ≥ 0), costing a point.

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 deterministic numeric tool with an output schema (so return values need not be described), everything an agent needs — formula, unit conventions, type formats, bounds, rounding, precision, error semantics — is present.

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 0%, so the description carries the full burden, and it does: future_value and rate are Decimal strings, rate bounds and example given, periods constrained to integer ≥ 1, decimals defaults to 2 and must be a non-negative integer, rounding defaults to HALF_EVEN. All five parameters get meaning beyond their bare titles.

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 ('미래 현금흐름의 현재가치를 계산한다') and pins it down with the exact formula PV = FV / (1+r)^n, which unambiguously separates it from the inverse sibling finance.fv even though that sibling is not named.

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?

Gives real usage constraints (rate is a per-period rate ≥ 0 such as 0.05, periods an integer ≥ 1, and an explicit warning not to mix an annual rate with monthly periods), which tells the agent how to call it correctly. It does not, however, route the agent to alternatives such as finance.fv or finance.npv for the inverse or multi-cashflow case.

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