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

With no annotations, the description carries the full burden. It usefully clarifies that this returns a signing payload rather than performing a state change or payment, and that the challenge is bound to a specific proposal/offer version/price/payout. It omits challenge lifetime, single-use/replay behavior, and what the caller does with the result.

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?

Two short sentences, front-loaded with what is returned, followed by the authorization constraint and the signing caution. No filler; only the dangling 'prepared offer version' reference adds mild ambiguity.

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, yet the description never says what the challenge response looks like or how to submit it, and three required parameters are undocumented. Sufficient to understand intent, insufficient to actually drive the call in a multi-step signing flow.

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 0%, so the description must compensate and it does not: requestId, buyer and proposalId are never mentioned. It even refers to an 'exact prepared offer version' that has no corresponding parameter, leaving the mapping from inputs to the bound terms unexplained.

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 ('Return an EIP-191 challenge' for selecting a buyer request offer) and names what the challenge binds. It is distinguishable from select_buyer_request_offer and from create_buyer_request_challenge, though it never explicitly says which sibling consumes the returned signature.

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?

'Only the original buyer can select' and 'Inspect terms before signing; this is not payment' give the caller a precondition and a caution. But there is no explicit routing to the sibling that completes the selection (select_buyer_request_offer) or to the offer/proposal lookup needed first, so the sequencing is only implied.

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