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

Annotations already declare readOnlyHint=true, destructiveHint=false, so the safe-computation profile is covered. The description adds real value beyond that by documenting the sign convention of the result (negative = pay, positive = receive), which is not derivable from annotations.

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 tight sentences with the purpose front-loaded, followed by usage triggers and return semantics. No filler; every clause carries information.

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 correctly compensates by naming the returned fields and their sign convention. Params are largely self-documented, so the main gap is minimal – an agent has enough to call it correctly.

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 83%, with required params (side, sizeBase, entryPrice, fundingRate, days) and the contractType semantics already documented in the schema. The description adds no per-parameter detail beyond what is in the structured fields, so baseline 3 applies.

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: calculating total funding cost/income for holding a perpetual futures position. The title and description align and the scope is unambiguous. It does not explicitly distinguish itself from close siblings like run_funding_breakeven or run_compound_funding, but the holding-period framing is distinctive enough.

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?

Gives concrete trigger phrasing ("how much funding will I pay holding X days?", "is funding eating my profit?"), which tells an agent when to reach for this tool. It stops short of naming alternatives or conditions where another funding-related tool should be used instead.

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