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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds substantial behavior beyond that: explicit refusal of XAU/XAG/XPT/XPD and crypto, validation that entryPrice and units must be above zero, the deliberate non-rejection of exit prices at or below zero, and the pip/lot conventions used internally.

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 core purpose, then boundary rules, then return shape — a sensible order with almost no filler. It loses a point for redundancy: the precious-metals refusal list (XAU, XAG, XPT, XPD) is stated twice, and the 'The pair is BASE/QUOTE…' sentence begins mid-stream with an awkward capital, breaking the flow of the edge-case list.

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?

No output schema exists, yet the description supplies the return shape (scenarios[] with deltaPips, exitPrice, pnlQuote), the domain constants needed to sanity-check results (pip = 0.01 for JPY quotes, 0.0001 otherwise; standard lot = 100,000 units), and an explicit not-covered list. Nothing an agent needs to call this correctly or interpret the result is missing.

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 the baseline is 3; the description earns above baseline by resolving the one genuinely dangerous ambiguity — deltasPips are signed by actual price direction and are not pre-adjusted for side — and by pinning pair format (BASE/QUOTE, two distinct ISO 4217 codes, any letter case). It does not add per-parameter detail on units rounding or what precision entryPrice is accepted at.

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 — PnL across a range of hypothetical price moves in pips for a single forex position size, long or short. The 'hypothetical/what-if' framing cleanly separates it from sibling tools like workflow.run_forex_pnl (actual PnL) and workflow.run_forex_pip_value, so an agent can route without opening either 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 phrase ('Use when user asks "what if price moves X pips in either direction?"') plus clear exclusions: precious metals and crypto tickers are refused, and spread/commission/swap/slippage/account-currency conversion are out of scope. It stops short of naming the sibling to use instead for realized PnL or pip-value lookups, so the alternative routing is implicit rather than spelled out.

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