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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds valuable behavioral context: the meaning of status and review_status values, the _untrusted field for seller-provided content, and the same_human tier for rating. This goes beyond what annotations provide.

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 dense but well-organized, front-loading the core purpose and then explaining the nuanced fields. It's a single paragraph that packs a lot of information without being bloated. The structure could be slightly improved with bullet points, but it's effective.

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 read-only list tool with one optional parameter and no output schema, the description is quite complete. It explains the key fields, statuses, and how to use the results (with rate()). It doesn't describe pagination beyond limit, but that's a minor gap given the tool's simplicity.

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 coverage is 100% and the only parameter, limit, is fully described in the schema. The description doesn't add much about the parameter itself, but it does clarify the ordering ('newest first') which aligns with the schema's description. Baseline 3 is appropriate.

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 tool returns the user's purchases, newest first, with a detailed list of included fields. It distinguishes itself from siblings like mySales, myListings, and myReviews by focusing on purchases and their review statuses.

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 explains the context: it requires the user's API key and is for viewing purchases. It doesn't explicitly say when to use this vs. alternatives like mySales or myReviews, but the detailed field list makes the use case clear. It also mentions using purchase_id with rate(), which is a helpful cross-tool usage note.

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