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

With no annotations, the description carries the full burden and does well: it discloses the monetary cost model ($0.005 USDC per call via x402) and the return composition (sorted ranking, cheapest chain, chains that could not be queried). It stops short of stating failure modes or whether the x402 payment is required upfront.

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?

Front-loaded with the motivating question, then a compact sentence covering operation, inputs, and return, ending with pricing. No wasted clauses, though the leading question is slightly verbose next to the denser second sentence.

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?

For a 2-param read tool with no output schema and no annotations, the description covers the essentials: what it computes, the return shape, and the cost. Missing only minor details like supported chain coverage or latency, which an agent can tolerate.

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% and both parameters are enums, so the schema already documents valid values. The description restates the enum sets (transfer/usdc_transfer/swap and slow/standard/fast) without adding semantics such as what distinguishes tiers in practice. 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?

The description names a specific action (ranks chains by USD cost) and resource (transaction types across chains/speed tiers), and the opening question makes the intent unambiguous. It does not explicitly differentiate itself from the sibling get_gas_price, so the agent must infer that this tool compares across chains rather than fetching a single price.

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?

"Where is it cheapest to send this transaction right now?" implies the use case (cost-comparison before sending) but offers no explicit when-to-use vs. when-not, and never mentions get_gas_price as the single-chain alternative. The framing is helpful context rather than routing guidance.

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