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

Annotations only declare readOnlyHint and openWorldHint; the description adds real behavior the agent cannot see elsewhere — a 10-second cache, a metered cost of $0.003 per call, and the x402 payment rails (USDC on Base or Solana). It stops short of describing not-found/error behavior or how many transfers are returned for a busy transaction.

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?

Short, front-loaded sentences with the resource and returned fields first, followed by invocation guidance and then cost/caching notes in the order an agent would need them. The opening sentence largely repeats the tool title and the return-field list is restated at slightly more length than necessary, but there is no filler.

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 responsibility for describing the response, and it does so by enumerating status, confirmations, block time, fee and decoded ERC-20 transfers. Pricing, caching and chain fallback are also covered; only failure modes and transfer-list limits are left implicit.

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 all three parameters are already documented, and the schema fixes the default for chain to an empty string. The description restates the empty-chain semantics in plain language, which is useful but does not add syntax or format detail beyond what the schema already supplies.

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?

Names a specific resource (an EVM transaction identified by hash) and enumerates what is returned: status (pending/success/failed), confirmations, block time, fee and decoded ERC-20 transfers. That is enough to separate it from siblings like evm_address, evm_balance and evm_call, though the description never explicitly contrasts with them.

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?

"Use to verify a payment arrived" gives one concrete situation in which to pick this tool, and "Leave chain empty to search all supported chains" tells the agent how to invoke it under uncertainty. There are no when-not-to-use rules and no named alternative for cases where the hash is unknown or the chain must be pinpointed.

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