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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the description's job is to add substance, which it does by disclosing the degradation behavior: 'Missing metadata and prices are marked unavailable.' It also implies the response shape (resolved ABI method vs raw selector fallback). It doesn't mention the paid x402 flow ($0.003 in the title), letting the payment parameter carry that.

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?

One dense, front-loaded sentence that leads with the trigger and then the payload. Every clause maps to a real returned field, but the run-on enumeration of nine items is slightly hard to scan compared with a short bulleted list.

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?

There is no output schema, so the description carries the burden of describing the return value, and it does list the major fields plus the fallback for missing data. Remaining gaps are minor for a read-only lookup: nothing on invalid-hash errors or response format (JSON vs text).

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% and every parameter (tx, chain enum, payment, holderWallet) is documented in the schema itself. The description adds only that both Ethereum and Base are supported, which the enum already states. Baseline 3 is appropriate when the schema does the heavy lifting.

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 verb (explain/understand) and resource (Ethereum or Base transaction) and then enumerates exactly what the explanation contains: receipt, confirmations, block/time, sender, recipient, resolved method or raw selector, token transfers, gas in ETH and USD, and a plain-English line. That is unmistakably distinct from siblings like gas_now, wallet_check, or token_verdict.

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?

Opens with an explicit trigger: 'Use when an agent needs to understand an Ethereum or Base transaction.' It does not name a sibling alternative or a when-not condition, but the trigger condition is concrete enough that an agent can route to it without inference.

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