Estimate eToro trading costs

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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the bar is lower, yet the description adds real value: it confirms nothing is placed, enumerates the fee components computed (markup, spread, transaction, overnight/weekend, stamp duty), and specifies amounts are in USD. It omits any statement about return shape or latency, but the added context is solid.

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?

Three short sentences, front-loaded with the purpose and the compute-only guarantee, then the currency unit and the closing hint. No filler.

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 9-parameter tool with zero schema descriptions and no output schema, the description is thin: it names the output fee components and currency but leaves nearly all input semantics undocumented, so an agent must infer which parameters pair with which action (open vs close) and what values are valid.

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 0% across 9 parameters, so the description carries the full burden. It only clarifies one parameter ('For closing, pass the position ids') and never explains action, symbol, leverage, amountUsd, orderType, transaction, instrumentId, or settlementType — enums and defaults exist in the schema but no semantics are added.

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 — a what-if cost breakdown for a hypothetical order — and immediately clarifies 'Computes only; places nothing', which cleanly separates it from the read-only portfolio/pnl/balance siblings and from any order-placement flow.

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 'what-if ... hypothetical order' framing plus 'Computes only; places nothing' tells the agent this is for estimation rather than execution, and 'For closing, pass the position ids' gives a concrete conditional. It stops short of naming an alternative tool or stating exclusions explicitly.

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