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

Given readOnlyHint=true is already present, the description still adds valuable behavioral detail by stating 'Returns unsigned calls; never signs or submits.' This clarifies the non-submitting, non-signing nature beyond the annotation's generic safety signal.

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, front-loaded sentence that introduces the primary function, a precondition ('exact ETH value for a current listing'), and the key non-side-effect ('never signs or submits'). 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?

For a preparational tool with an output schema and annotations already covering safety, the description provides sufficient context. The only minor gap is not explicitly distinguishing between mainnet and internal market variants, but the tool name and title help cover that.

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%, so the baseline is 3. The description adds meaningful context by requiring the exact ETH value for a current listing, which clarifies that priceWei is not arbitrary and must be tied to the currently listed price. This goes beyond the schema's generic decimal-like string description.

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 identifies a specific operation: prepare buy() with the exact ETH value for a current listing. It clearly distinguishes this from the broader sibling set by focusing on mainnet purchase preparation and by adding that it returns unsigned calls and never signs or submits.

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 when to use the tool by mentioning 'a current listing' and 'exact ETH value', but it does not explicitly compare with similar siblings like prepare_internal_buy, prepare_mainnet_offer, or prepare_purchase. There is useful context, but no concrete when-not/alternatives guidance.

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