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

No annotations, so the description carries the full burden, and it delivers: read-only semantics, no signing/sending, pricing ($0.001 per call), payment mechanisms (x402 USDC on Arc/Base/Solana, XNT on X1), and a two-call x402 handshake. This is rich behavioral context an agent cannot infer from the schema.

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 dense sentences, front-loaded with the core action and outcome, then payment mechanics. No filler; every clause conveys operational information.

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, and the description compensates by naming the return (bytes or revert reason). Combined with the payment flow and no-signing disclosure, an agent has everything needed to call correctly across the two-step x402 purchase.

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 100%, so baseline is 3; the description adds meaning beyond the schema by explaining the two-state `payment` parameter – call without it to get terms, call again with the signed payload to complete purchase. It does not add syntax for `to`/`data`/`from`/`chain`, but the payment semantics are the non-obvious part and are well explained.

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?

Specific verb+resource: 'Read-only contract call (eth_call)' with named chains, and clearly distinguishes itself from evm_tx by stating 'Nothing is signed or sent.' It also states the return value (bytes or revert reason), which siblings like evm_tx do not.

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?

Explicit two-step payment flow: 'Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.' This is exactly the when/how guidance an agent needs and is absent from all siblings.

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