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

Explains the otherwise-puzzling annotation readOnlyHint=false ('not marked read-only because each call is charged'), and adds pricing ($0.003/call via x402 USDC or card key), a free tier (first 25 free), that failed calls are free, and that an unknown hash returns 404 uncharged. These are behavioral facts no annotation conveys.

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?

Dense but front-loaded: purpose and returned fields come first, followed by routing rules, input format, example, and pricing. Every sentence carries information an agent needs; nothing is redundant padding.

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 itself enumerates the return fields, so the agent knows what comes back. Combined with the routing guidance, input format, and error/pricing behavior, nothing required to call the tool correctly is missing.

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?

Only one parameter and schema description coverage is 100%, so the baseline is 3. The description restates the 0x-prefixed 64-hex format consistently with the schema and adds a concrete example hash, which adds marginal value beyond the structured field.

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 a specific verb and resource ('Look up a Ethereum transaction by hash') and enumerates exactly what is returned: sender, recipient, value in ETH, nonce, gas limit, function selector, and block. It explicitly distinguishes itself from the sibling lookup tools eth_receipt and eth_logs, so an agent can route without opening either 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?

Gives explicit when-to-use and points to named alternatives with their selection criteria: 'for success or failure and fees paid use eth_receipt, for emitted events eth_logs'. This is a complete routing rule rather than implied usage.

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