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

Annotations only declare read-only, open-world, non-idempotent, non-destructive; the description adds the billing model ($0.01/call, 25 free, failed calls free, repeats charged), which explains and is consistent with idempotentHint=false. It also discloses the miss path (404, uncharged) and restates the no-side-effects guarantee.

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 its payload, then the alternative, then input/error semantics, then cost. Dense but every clause carries decision-relevant information for an agent that will be charged per call.

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 receipt fields returned. For a single-parameter, read-only, billed tool, nothing an agent needs to call it correctly or interpret the result 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?

Schema coverage is 100% and the single parameter is already documented, so the baseline is 3; the description goes further by supplying a concrete example hash and tying hash validity to the 404 outcome. It stops short of explaining hash casing or malformed-input behavior.

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+resource — fetch an Optimism transaction receipt — and immediately enumerates the returned facts (status, gas used, effective gas price, fee in ETH, log count, contract created). It also names the sibling it is not (op_tx) with the payload it does not cover, so an agent can separate the two without opening schemas.

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 an explicit use case ("confirm a payment or call went through") and an explicit alternative with the condition that selects it ("for sender, value and calldata use op_tx"). Pending/unknown hashes are routed to a defined outcome (404) rather than left ambiguous.

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