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

Annotations already mark it read-only and idempotent, and the description adds useful behavioral context: it uses a constant-rate scenario rather than live data, and it defines the funding sign convention ('Positive funding: longs pay shorts'). This goes beyond what the annotations alone provide.

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 three short sentences with no filler, front-loads the outputs, and adds two high-value caveats: the funding sign convention and the constant-rate scenario. Every sentence earns its place.

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 tool has no output schema and a high parameter count with sparse schema descriptions, so the description should clarify output meaning and units. It lists the outputs but does not specify units or the precise meaning of 'linear break-even move,' leaving some ambiguity for an agent deciding how to interpret 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 description coverage is only 20%, so the description should compensate for missing parameter documentation. It does add meaning by clarifying the funding sign convention and the constant-rate nature of the rate parameter, but it does not explain the role of notional_usd, side, settlements, or round_trip_fee_bps in any detail.

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 names the specific computation: perpetual funding cashflow, fees, net carry, and linear break-even move, and the title adds the verb 'Calculate.' It clearly identifies a financial calculation tool rather than a data-retrieval or monitoring tool, though it does not explicitly distinguish itself from sibling tools like exit_cost.

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 description gives clear context: this is for caller-provided parameters under a constant-rate scenario, explicitly not live rates or a forecast. This is enough for an agent to know when to use it, though it does not name specific alternatives or state explicit 'use this instead of X' guidance.

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