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

With no annotations, the description carries the full load and does reasonably well: it discloses the critical non-behavior (no payment, no purchase completion) and the fact that payment needs separate authorization. It omits idempotency, what happens on signature failure, and any permission/expiry semantics around the signed challenge.

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 sentences, no filler, and the returned-value information plus the payment caveat are front-loaded where the agent needs them before deciding to 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?

For a signing/mutation tool with no annotations and no output schema, the description usefully summarizes the return payload and the non-payment guarantee. However, with all three params at 0% coverage and no prerequisites or failure modes stated, an agent still lacks enough to construct a correct call from the description alone.

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% for three required parameters (requestId, challengeId, signature), so the description must compensate and does not. Only "buyer-signed" loosely hints at what signature means; requestId vs challengeId and their relationship to the selection flow are entirely undocumented.

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?

Specific verb plus resource: completes the buyer-signed selection for a proposal offer and states what it returns (prepared-artifact checkout path and buy_prepared_artifact arguments). That distinguishes it from propose_buyer_request_offer and buy_prepared_artifact, though it never names those siblings directly, so an agent must infer the boundary.

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?

"Payment requires a separate authorization; this tool never pays or marks a purchase complete" is an explicit exclusion that steers the agent away from using this as a pay step, and the return of buy_prepared_artifact arguments implies the follow-up call. It does not address when to use this versus complete_buyer_request or the proposal step, so routing is only partly covered.

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