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

Goes well past the annotations by spelling out the write mapping (loved → favorites with reason, disliked → books to avoid, loved/read not yet shelved → Finished), the non-destructive guarantee for existing shelf/rating/note data, and where unmatched titles land. That is exactly the causal detail an agent needs before performing a mutation that annotations only label as non-destructive and idempotent.

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 core action, cap, and output mapping are front-loaded in the opening sentence, and every following clause adds a new constraint rather than repeating. It is dense, with several clauses chained by semicolons, which costs a little readability but no sentence is wasted.

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 mutation tool with a single nested-array parameter, no output schema, and low schema description coverage, the definition covers inputs, side effects, and the key return detail (unmatched titles). The per-book result shape beyond "unmatched" is not described, which is the one thing an agent must discover by calling.

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 reported at 0%, so the description has to carry the load, and it does explain the meaning of each feeling value in prose despite the bare enum (loved/disliked/read) and shows what "why" is for via the "for its humor" example. It does not restate the 200-character limit or the accepted identifier formats for "book", which the schema already covers, so a small gap remains.

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?

Names a specific verb and resource ("Save books ... into their taste") plus the scope ("up to 25 at once") and the three input categories it handles. It explicitly distinguishes itself from add_to_library, so an agent can pick between the two without opening either 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?

Gives the selecting condition against a named alternative: "Never changes a shelf, rating or note they already have; add_to_library does that." It also states the prerequisite ("Needs a linked Siftivo account") and the batch cap, which are the practical gates on calling it.

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