calculate_position_size

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

With no annotations, the description carries the full burden and does so excellently. It details the calculation steps, fee deduction, rounding down based on LOT_SIZE/MIN_NOTIONAL/PRICE_FILTER, the FILTER_VIOLATION fail-closed return, and active validation checks (stale price, wrong stop direction, unknown symbol, insufficient balance).

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 description is two sentences, densely packed with essential information. Each sentence earns its place: the first covers the calculation and rounding, the second covers validations and error behavior. There is zero waste.

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?

The description comprehensively covers the algorithm, failure modes, and validation for a calculation tool. The lack of an explicit success return format (since no output schema exists) is a minor gap, but the behavioral details largely compensate.

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 only 44%, but the description compensates by explaining the roles of core parameters (account_balance, risk_pct, entry, stop_loss, fee_rate) in the formula. It also adds context about rounding and error behavior. Metadata parameters like request_id and idempotency_key are not explained, but they are straightforward.

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?

The description clearly states the tool calculates risk-based position size with a specific formula (account_balance * risk_pct divided by risk-per-unit, fee deducted, rounded down by exchange filters). It distinguishes itself from order execution tools by focusing on the calculation aspect and mentioning validation and error handling.

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 usage is implied: it computes position size before trading. However, there is no explicit comparison to sibling tools like place_order or place_oco_order, nor any exclusions. The description does not explicitly say 'use this when' or 'don't use when'.

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