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

Annotations already cover read-only and open-world safety, so the description's job is return-content disclosure, which it does well: it describes the cost decomposition (fees plus live-book slippage), fee tier, book time, and critically that some venues return no figure with an explanation. That last clause prepares the agent for partial results, which is real behavioral value. It does not mention rate limits, data freshness, or ordering in detail.

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?

A single dense sentence that front-loads the core output (round-trip cost ranking) before the supporting fields. Every clause carries information and nothing is redundant with the title, though the parenthetical and trailing list make it slightly harder to scan than a two-sentence split would be.

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 and a simple three-parameter input, the description carries the return-value burden and does so by naming the output fields and the partial-coverage case. What's missing is how the ranking is ordered or expressed (bps, absolute USD) and how quickly live book data goes stale, which matters for a real-time slippage estimate.

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 100%, including the enum of supported pairs, the minimum order size, and the monthly_volume_usd fee-tier mechanism. The description's mention of 'fee tier' and 'book time' aligns with the schema but adds no format, units, or default detail beyond it. Baseline 3 is appropriate.

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 resource and action: a full ranking of round-trip cost (fees + slippage on the live book) of a market order across perp DEXes. This is clearly a cost-comparison tool rather than depth, funding, or execution planning. It stops short of naming siblings like best_venue or execution_plan to sharpen the boundary, so 4 rather than 5.

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 phrase 'Full ranking ... on each perp DEX' implies the use case of comparing venues before trading, but there is no explicit when-to-use, when-not-to-use, or pointer to the obvious alternative best_venue for a single recommendation. Usage is inferred rather than stated.

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