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

Annotations declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description adds genuine behavioral context beyond that, notably that relative dates must be resolved against the `today` block returned by this tool, bank_holidays, or is_business_day_check. It also spells out the settlement conventions (T+0/T+1/T+2, D+1) that govern the result, though it does not discuss error behavior for invalid country codes or unsupported pairs.

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 is front-loaded in the first line, followed by a compact factor list and four illustrative calls; every element earns its place. The examples section is slightly long relative to the core content but remains skimmable and informative.

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 an output schema present, return values need no explanation, and the read-only annotations cover the safety profile. The description is largely complete for a 6-parameter computation tool, with the main residual gap being no explicit differentiation from adjacent siblings like settlement_eta and fx_timing_advisor.

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 schema already documents all six parameters including defaults and the FX-required currencies. The description's examples add positional-argument ordering (value_date("US", "DE", "fx_spot", "USD", "EUR")), which is a mild bonus over the schema, but it introduces no new semantics for individual parameters.

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: calculating the value/settlement date for a payment, with the inputs that drive the result (holiday calendars, weekend conventions, settlement convention). Clear enough to distinguish from pure holiday/calendar lookups like bank_holidays or is_business_day_check, though it never explicitly contrasts itself with the close-sounding sibling settlement_eta.

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 bullet list of contributing factors and the four worked examples imply when the tool applies, and the settlement_type options give concrete usage modes. However, there is no explicit when-to-use/when-not statement and no routing to alternatives such as settlement_eta, payment_cutoff_times, or bank_holidays, leaving the agent to infer the boundary.

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