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

Annotations already cover read-only, non-destructive, open-world, and non-idempotent; the description adds genuinely new context: pricing ($0.01/call, first 25 free, failed calls free), that repeat calls are re-charged (explaining the non-idempotent hint), and the limited decode scope ("common ERC-20, ERC-721, WETH, permit and multicall"). It does not discuss rate limits or what happens on unknown/non-decodable calldata beyond implying graceful fallback.

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?

The core capability is front-loaded in the first sentence, with use case, example, pricing, and safety follow-ups in descending priority. It is dense and slightly long, but nearly every clause carries information an agent needs; the pricing sentence is a bit promotional in tone.

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 does the work of explaining the return contents in detail (decoded function, transfers with amounts and symbols, summaries), plus chains, cost, and safety. What is missing is failure-mode behavior for exotic calldata or unverified contracts, which matters for a decoding tool.

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%, with both hash and chain fully documented including the default and the five network aliases, so the schema carries the parameter burden. The description only restates the chain set and adds a worked hash example, which adds marginal value at best.

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?

States the specific action (explain an EVM transaction) and enumerates exactly what the output covers: status, sender/contract, ETH value, fee, decoded function, token transfers/mints/burns/approvals plus one-line summaries. It also names the supported chains, which distinguishes it from the per-chain siblings (base_tx, eth_receipt, arb_tx, etc.) that return raw data rather than a decoded narrative.

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 check what a payment or contract call really did before trusting it or reporting it" gives a clear verification-before-reliance use case, and the example hash shows the intended call shape. It does not explicitly name the raw alternatives (e.g., base_tx, evm_decode_calldata) or say when raw data is preferable, so routing is implied rather than stated.

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