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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses critical behavioral details: that quotes are indicative (not executable), the cost ($0.002 per successful call), the payment mechanism (x402 on Base, Solana or Arc), and that failed calls are not charged. This adds substantial value not captured by 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?

The description is a single dense paragraph that is front-loaded with the core purpose and key caveats. It is efficient but could be slightly more structured (e.g., separate pricing details) for faster scanning.

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?

Given the presence of an output schema, the description still provides a comprehensive preview of return values (amount out, USD values, gas, price impact, pools/DEXes, which aggregator gives more). It also covers chain support, cost, payment, and failure behavior, leaving no critical gaps for an agent 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 100%, so parameter meanings are already well-documented in the schema. The description only reiterates the chain list and confirms tokenIn/tokenOut can be native or contract addresses, adding marginal value beyond the existing schema.

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 states a specific verb ('Best swap quote') and resource ('for a token pair on an EVM chain'), and explicitly names the compared aggregators (KyberSwap, Velora/ParaSwap). It distinguishes itself from single-DEX routing siblings like sushiswap_route_quotes by virtue of being an aggregator comparison tool.

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?

It provides clear context: 'Indicative quotes, not executable orders' and lists supported chains. However, it does not explicitly name an alternative tool or state when to use this over a single-DEX quote tool, leaving some inference to the agent.

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