List what the user picked

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

The annotations already indicate read-only, idempotent, and non-destructive behavior. The description adds context beyond those annotations: empty results until confirmation, the ~1-hour expiry of base_url, and the need to use download_picked for actual bytes. This is exactly the kind of behavioral disclosure that helps an agent act safely.

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 compact and front-loaded: the core purpose appears first, followed by the prerequisite call, then the crucial download guidance. Every sentence earns its place and no filler is present.

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 100% schema coverage, the description covers the non-obvious return behavior (empty until confirmed), the expiring base_url, and how to access actual bytes. No output schema exists, but the key behavior an agent needs to call and interpret this tool correctly is present.

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?

All four parameters are already fully documented in the input schema, including session_id's origin from start_pick_session, pagination with next_page_token, and account selection. The description does not add parameter-level meaning beyond the schema, so the baseline of 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 states a specific verb and resource: 'Return the media items the user selected in a picker session.' This clearly distinguishes the tool from library search, album listing, and item download, and is consistent with the title.

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 explicitly tells the agent to call check_pick_session first and explains that the result is empty until selection is confirmed. It also routes actual byte retrieval to download_picked rather than exposing the expiring base_url directly, giving clear when-to-use and when-not-to-use guidance.

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