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

Annotations only cover the safety profile (readOnlyHint, openWorldHint). The description adds behavior an agent must know before calling: it is pay-per-use at $0.005 USDC via x402, it draws decoded signatures from public databases, and it flags unlimited approvals. Cost and payment mechanism are material operating facts not derivable from any structured field.

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 core action and output inventory in a single dense sentence, ending on the chain list and price. Efficient overall, though re-listing the chains already present in the schema is marginal payload.

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 exists, and the description compensates by enumerating the returned fields (function, tokens, NFTs, approvals, events, status, fee in native and USD). Combined with chain coverage, price, and payment rail, an agent has everything needed to invoke 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 coverage is 100% and both parameters (hash, chain) are already documented with the chain default and allowed values. The description restates the chain set (Base, Ethereum, Arbitrum, Optimism, Polygon) but adds no format or semantics beyond the schema, so the 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?

Specific verb ('explain') plus resource ('any EVM transaction') and an explicit inventory of what the explanation contains: decoded function, token flows, NFT moves, approvals (with unlimited flag), events, status, and USD/native fee. An agent can distinguish it from decode-only siblings like abi_decode or simulation tools like tx_simulate 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?

'Explain any EVM transaction' implies post-hoc, human-readable interpretation of an already-mined tx, which implicitly separates it from tx_simulate. However, no sibling is named and there is no explicit when-not guidance, so the routing signal is left to inference rather than stated.

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