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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower; the description nonetheless adds real behavioral context: swap rates are broker-set with no free live feed, so swapPerLotPerNight is always a manual input quoted per standard lot, and the sign convention (negative=cost, positive=credit). It does not need to explain return format beyond the field list it already gives, but it stops short of noting anything about precision/rounding.

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 purpose, then the manual-input caveat, sign convention, sibling disambiguation, trigger phrase, and return fields – well ordered and each sentence carries information. Slight redundancy with the schema on the negative/positive convention keeps it from a 5.

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 4-required-parameter computation tool with no output schema, the description supplies the missing pieces: currency context for the result, the manual-input rationale for the only non-obvious parameter, the sign convention, the sibling routing rule, and the returned field list (lots, totalSwapQuote, base, quote). An agent has everything needed to call and interpret it.

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 is 3; the description earns above that by explaining why swapPerLotPerNight is manual (no live source), that it is quoted per standard lot and mirrors how commission is quoted in workflow.run_forex_breakeven, and by reinforcing the negative/positive sign semantics. This adds genuine meaning beyond the schema text.

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 ('total swap/rollover cost for holding a forex position overnight') with the unit of account (pair's own quote currency) and explicitly names the sibling it is not (workflow.run_forex_swap_cost_live). An agent can distinguish it from the many other forex workflow tools 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?

Gives an explicit trigger ('Use when user asks "how much will holding this position overnight cost me?"') and a routing rule to the alternative ('The live variant ... applies when the account currency differs from the pair's quote currency'). Both when-to-use and when-to-use-the-other are covered.

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