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

Annotations already indicate destructiveHint=true and readOnlyHint=false, so the tool is known to be a write with side effects. The description adds valuable context about pricing (paid read-premium), routing constraints (hosted accountless write blocked), and signer boundaries. No contradiction with annotations.

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 excessively verbose with SAP-specific context that is repeated in the input schema description. The first sentence is clear, but the rest adds noise and redundancy, reducing conciseness. It could be trimmed to essential guidance.

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 presence of an output schema (not shown but noted), the description covers the basic operation and some behavioral notes (pricing, routing). However, it lacks a succinct summary of what the tool returns or its prerequisites, relying on the SAP jargon that may not be universally understood. Completeness is adequate but not ideal.

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?

Both parameters (buyer, listingId) are documented in the input schema with descriptions. Schema coverage is 100%, so baseline is 3. The description does not add further meaning to these parameters beyond what the schema provides.

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 'Purchase an NFT from a 3.Land listing' as the core purpose. It also mentions its role within broader 3.Land flows, providing context. However, it does not explicitly differentiate from sibling tools like 3land_listForSale or 3land_mintAndList, though the action is distinct enough.

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 advises confirming marketplace price, seller/buyer wallet, collection, and listing state before writes, which serves as a precondition. It does not explicitly state when to use this tool over alternatives, but the purpose and sibling names make it reasonably clear. The guidance on pricing and routing is present but more SAP-specific than general usage.

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