Retrieve 'Customers Also Bought' books from the Apple Books catalog using a numeric book ID. Optional language and country parameters refine results to show relevant related titles.
Retrieve "Customers Also Bought" books. Returns the related books shown on the Apple Books catalog page.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Apple Books numeric book ID | |
| lang | No | Result language tag | |
| country | No | Two-letter storefront country code |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description carries the full burden. It discloses that the tool returns related books from the Apple Books catalog page, which is useful, but it omits behavioral details such as pagination, result limits, ordering, or how lang and country affect results. This is acceptable for a simple read-only lookup but not rich.
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 two concise sentences with the key verb and resource front-loaded. There is no filler or redundancy, and each sentence contributes either the primary purpose or the source context.
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 low-complexity retrieval tool with full schema coverage, the description adequately conveys what is returned and from where. It lacks explicit mention of the output shape or list behavior, and since no output schema exists to offload that, this is a minor but not critical gap.
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?
The input schema already provides descriptions for all three parameters (100% coverage), including the numeric book ID, language tag, and two-letter storefront country code. The description adds no parameter-specific meaning beyond the schema, so it meets but does not exceed the baseline.
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 uses a specific verb, 'Retrieve,' and identifies the resource as 'Customers Also Bought' books from the Apple Books catalog page. This clearly distinguishes it from sibling tools like apple_books_book (detail lookup), apple_books_book_reviews, and apple_books_audiobook_similar.
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 implies the usage context through the 'Customers Also Bought' phrasing, but it does not explicitly state when to choose this tool over alternatives or when not to use it. There are no exclusion or alternative mentions, though a user can reasonably infer this is for finding related books from a specific book ID.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.