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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely non-obvious context beyond them: the aggregator behind the quote, the five supported chains, and a concrete per-call cost ($0.003 USDC via x402). It does not mention quote staleness/slippage validity, which would matter for a price quote.

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 compact sentences, front-loaded with the core value proposition and ending with the cost constraint. The chain list ('Base, Ethereum, Arbitrum, Optimism, Polygon') partially duplicates the chain parameter's schema description, which is mild redundancy but not bloat.

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 carries the return-value burden and does so by naming the fields returned (amount out, USD values, price impact, gas cost, route). Parameters for tokens and chains are addressed, and the x402 payment requirement is disclosed. What is missing is minimal — e.g., whether the quoted route can be passed onward to a build/execute step.

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 50% — to_token and from_token carry no schema descriptions. The description compensates by stating tokens may be given by symbol (ETH, USDC, USDT, WETH, DAI, WBTC) or by address, and it restates the valid chain values. That fills most of the gap, though it doesn't clarify amount formatting beyond the schema's own example.

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 gives a specific verb and resource ('Best DEX swap price across every major exchange (KyberSwap aggregator)') and enumerates exactly what the quote returns: amount out, USD values, price impact, gas cost, route. It does not name the obvious sibling it must be distinguished from (swap_build, which presumably executes), so sibling differentiation is left to inference rather than stated.

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?

Usage context is implied ('how much you get for an amount') and the $0.003 USDC x402 payment requirement is a useful invocation condition. However, there is no explicit when-to-use/when-not guidance and no routing to swap_build for actually executing the swap or to bridge_quote for cross-chain moves.

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