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

Annotations already declare readOnlyHint=true, idempotent and non-destructive, and the description reinforces that it places no order. It adds genuinely new behavioral detail beyond the annotations: rounding down to the venue step, capping by every limit, and self-fetching equity, price and contract rules. It stops short of describing failure behavior (wrong-side stop, insufficient equity, venue mismatch), which keeps it from a 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?

Front-loaded with the core transformation, then the ordering constraint, then the input-uniqueness rule, then a compact example. Every clause carries operational information; nothing is redundant padding.

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 an eight-parameter, anyOf-constrained sizing tool this covers the essentials: what it computes, what it reads, what caps apply, what it is not, and the exact next call. Since an output schema exists, it correctly avoids explaining return values while still pointing at preview_args from the result.

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 would be 3, but the description adds real meaning: stop_loss and stop_distance_pct are alternatives (give one), and risk_pct_of_equity versus notional_usd are alternatives, with omission defaulting to the maximum the limits allow. The worked example JSON anchors the units for stop_distance_pct and risk_pct_of_equity.

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 precise transformation: risk percentage plus stop distance becomes a base-coin size, rounded down to the venue step and capped by limits. This is a specific verb+resource that cannot be confused with siblings like preview_order or get_my_risk_limits, and it names what it reads internally (equity, price, contract rules).

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?

Explicit sequencing: use before preview_order, then preview and execute afterwards, with preview_args from the result as the handoff. It also warns that this is not an order and instructs the caller to supply the stop once and the amount once, which prevents the most likely misuse.

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