Live execution cost: what a market order really costs

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

Annotations already mark it readOnly and openWorld, and the description adds meaningful behavior: it uses the full visible order book, excludes fees, and explains that null means the book cannot absorb that size. That gives an agent enough behavioral context to interpret edge cases correctly.

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?

Two dense sentences with no wasted text. The usage trigger is front-loaded, followed by return scope and important exclusions, so an agent can act on the first sentence and refine interpretation with the second.

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?

No output schema exists, but the description explains the return shape well enough: basis-point cost ladders, sizes from $10K to $5M, both sides, 8 perps, fees excluded, and null semantics. It is nearly complete for a read-only no-parameter tool, though it does not mention response formatting or ordering details.

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?

There are zero input parameters, so parameter semantics are inherently minimal and the baseline is 4. The description does not need to explain parameter formatting, but it usefully clarifies the size range and market coverage that shape the result.

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 (slippage/cost for market orders) and scopes it to live execution cost across 8 major perpetuals, both sides, $10K to $5M. This clearly distinguishes it from a generic orderbook-depth tool by framing the output as cost ladders in basis points.

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?

Explicitly says when to call it: when the user asks how much slippage a trade would face, how thick the books are, or which major perp is thinnest. Those are concrete triggering conditions, not vague suggestions.

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