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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context beyond them: the output is a link, the cart is populated automatically, and the actual transaction happens elsewhere on starchild.music — a key behavioral boundary. It does not mention link lifetime, authentication, or the 10-item cap, keeping it at a 4.

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?

Three tight sentences, each earning its place: purpose first, checkout boundary second, parameter guidance third. No restatement of the name or title and no filler.

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?

With no output schema, the description does explain the return value as a link that opens a pre-populated cart, which is what an agent needs. The 10-item and 1-item bounds live in the schema, so they need not be repeated. Missing only minor operational detail such as link permanence or sharing semantics.

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 carry parameter meaning. It does compensate for the license field by naming concrete values (song-only, song-instrumental, royalty-free, exclusive-license) that the schema lacks an enum for. However, the required 'song' field is never explained — whether it takes an id, title, or slug is left to inference, leaving half the semantics uncovered.

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+resource ('Turn chosen songs and licenses into one link') and immediately clarifies the resulting artifact: a Starchild cart URL with items pre-added. It also names the sibling license_options as the source for license ids, so an agent can separate it from search_songs, license_options, and checkout flows without opening any schema.

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 establishes context ('Checkout happens on starchild.music') which implicitly tells the agent when this tool applies versus when it does not — this builds a link, it does not complete a purchase. It also directs the agent to license_options for valid license ids. There is no explicit when-not or named alternative for the overall workflow, so it falls short of a 5.

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