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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false), and the description adds genuinely new context absent from them: a $0.001 USDC-on-Base cost per successful call paid via x402. The payment detail also explains why readOnlyHint is false despite a lookup-style tool, so there is no contradiction.

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 resource and returned fields, then the use case, then pricing. The field enumeration is longer than strictly necessary but each element earns its place by compensating for the missing output schema. No filler sentences.

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 usefully enumerates the returned fields and discloses the x402 payment model, which is the key operational detail for this family of paid tools. It could go one step further on error behavior (e.g., what happens when the hash does not exist), which keeps it from a 5.

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?

With a single parameter at 100% schema description coverage, the schema already documents 'hash' as '0x transaction hash'. The description confirms the input is a hash but adds no format, validation, or lookup-failure semantics beyond the schema, so baseline 3 applies.

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 the exact resource (an Ethereum transaction identified by hash) and enumerates the fields it returns (sender, recipient, value in ETH, nonce, gas limit, function selector, block), making it clearly distinguishable from siblings like eth_receipt, eth_logs, and eth_block without opening any schema.

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 gives one concrete use case ('Use to check what a transaction did or whether it exists'), which implies when to reach for it, but never names a sibling alternative or an exclusion condition (e.g., use eth_receipt for status/gas-used). Usage is therefore implied rather than explicit.

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