Get book details

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

No annotations are provided, so the description carries the full burden for behavioral disclosure. 'Fetch' implies a read-only operation, but the description does not explicitly state that, nor does it describe the return format, error handling, or authentication requirements. It does disclose the significant nuance that for-sale and for-borrow copies have different IDs/SKUs, which adds useful behavioral context, but other operational details are missing.

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 concise at two sentences with no filler. The first sentence front-loads the main action and object, and the second sentence adds essential usage constraints and the borrow-copy caveat. Every clause earns its place; it is neither under-specified nor verbose.

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 or annotations, the description is the only source of contextual info. It clarifies the identifier selection and the sale/borrow nuance, which is strong. However, it does not describe what 'full details' includes (e.g., fields returned), and it does not address edge cases like supplying both id and sku. For a simple, single-resource tool, this is adequate but not complete; an agent might not know the exact shape of the response.

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 schema already describes both parameters fully (100% coverage), so the baseline is 3. However, the description adds valuable meaning beyond the schema: it explicitly states the mutual exclusivity of 'id' and 'sku', and it explains the SKU suffix '-L' for borrow copies, which is essential for correct input selection but absent from the raw schema. This elevates the parameter semantics.

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 ('Fetch') and a clear resource ('full details for a single book'), and it uniquely identifies the tool by requiring either a numeric ID or an exact SKU. It implicitly distinguishes itself from the sibling 'search_books' by focusing on a single book known by identifier, rather than a search across multiple results.

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 provides clear conditions for usage: you must know the exact numeric ID or SKU, and it explicitly states to provide exactly one of them. It notes the sale-vs-borrow distinction, which is crucial for selecting the correct identifier. However, it does not explicitly mention when to choose this tool over 'search_books' (e.g., when an exact ID/SKU is known), so the guidance is clear but not fully explicit about alternatives.

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