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

Annotations already declare readOnlyHint=true, openWorldHint=false, destructiveHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: it is a self-contained pure computation needing no live FX rate, and it enumerates the return fields (notionalQuote, marginQuote, base, quote). It stops short of stating units/precision conventions, hence a 4 rather than 5.

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?

The opening sentence and the alternative-tool sentence are well front-loaded and actionable. However, the sentence 'Never built for Phase 1 of this domain since a margin figure has no natural currency-neutral form the way pip value does' is internal design rationale that does not help an agent decide or invoke, weakening the signal-to-noise ratio.

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 no output schema, the description helpfully lists the returned fields and chains to the sibling variant. For a four-parameter read-only calculation this is nearly complete; only unit/tolerance conventions and the lots-vs-units question are left unaddressed.

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 all four parameters are already documented, which sets the baseline at 3. The example ('X lots ... at 50:1') loosely maps units and leverage, but it also introduces 'lots' while the schema says 'units in base-currency units' — an unreconciled mismatch rather than added clarity.

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: computes notional and margin required for a forex position, and pins down the currency form ('pair's own quote currency: no live FX rate needed'). It clearly distinguishes itself from the sibling workflow.run_forex_margin_required_live, so an agent can pick correctly 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 names the alternative (the _live variant) and the selecting condition ('when the account currency differs from the pair's quote currency'), and even supplies a concrete trigger query ('how much margin do I need for X lots of EUR/USD at 50:1?'). 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.