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

With no annotations provided, the description must carry the burden of behavioral disclosure. It states 'Instantly purchase' but does not detail side effects such as ETH transfer, token transfer, or any irreversible actions. It also does not disclose required approvals or prerequisites, which is significant for a purchase transaction.

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 description is a single, concise sentence that front-loads the action, resource, and method. It avoids unnecessary detail, making it easy to parse and remember, with no wasted words.

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?

Given the tool's complexity (a financial purchase with ETH) and the absence of annotations and output schema, the description is incomplete. It does not explain return values, error cases, or the need for approval, which are critical for agents to handle the transaction correctly and safely.

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?

Although schema coverage is 100% and the schema provides basic descriptions, the inclusion of 'priceInEth' as 'Optional expected purchase price for slippage protection' adds meaning beyond the schema by clarifying its purpose. The domainName and buyerAddress are self-explanatory, but the description adds context that the schema lacks, earning a high score.

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?

The description clearly states the action ('Instantly purchase'), the resource (an actively listed .i domain), and the method (from the secondary marketplace using ETH). It distinguishes itself from siblings like marketplace_make_offer and marketplace_accept_offer by specifying immediate purchase, making it easy for an agent to select the right tool.

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?

The description implies the tool is for buying a listed domain instantly, and the optional priceInEth parameter hints at slippage protection. However, it does not explicitly state when not to use it or mention alternatives like marketplace_make_offer for negotiating, which would be helpful for agents deciding between purchase and offer.

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