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

Annotations already flag this as a non-read-only, non-idempotent, potentially destructive operation, and the description adds crucial operational context: it produces a draft preview only, nothing is printed or charged, and the client cannot pass conversation images so `images` must be left empty (pictures are uploaded via an editor link in the result). It does not explicitly reconcile the destructiveHint=true label with the 'only the fields you pass change' partial-update behaviour, which would have closed the remaining gap.

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 most decision-relevant facts come first (what it produces, when to call it), followed by constraints and the non-billing reassurance. It is a fairly long block, but each sentence carries a distinct instruction; the only near-repetition is 'Never summarise or shorten it' reinforcing 'pass the text exactly as written'.

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 12-parameter tool with no output schema, the description covers the important operational unknowns: that the deliverable is a draft preview with an editor link, that pricing is only a display concern (country), and how images actually get attached. What remains unexplained is the return shape beyond the preview and how section-to-page mapping behaves for the two styles.

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 92%, so the baseline is 3, but the description genuinely adds meaning: partial-update semantics for book_id, the requirement to pass text verbatim and unsectioned-summary-free, and the instruction to leave `images` empty despite the schema's own description suggesting conversation pictures can be supplied. The style distinction (picture vs text) is left entirely to the schema enum description.

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 first sentence gives a specific verb ('lays out'), resource ('8.5-inch square book'), input sources ('story, memoir, letters or recipe collection'), and an observable outcome ('shows a page-by-page preview'). It is clearly distinct from the sibling create_print_order, which is the ordering step rather than the layout step.

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?

It names two explicit triggers (turn chat text into a book; change a book made earlier via book_id) and states the update semantics ('only the fields you pass change'). It also routes between content modes by pointing to sections vs full_text and explicitly forbids summarising.

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