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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered. The description adds behavior the annotations cannot express: null clears rating/status, an empty image_url removes the picture, and empty notes/dates/field values clear those attributes — exactly the destructive detail an agent needs before calling.

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?

Two sentences, front-loaded with the action and then the lookup rule, with no filler. The heavy parenthetical stacking of clearing rules makes it dense to parse but every clause carries information.

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?

Covers lookup and clearing semantics for a 15-parameter mutation tool with no output schema, which is most of what an agent needs. It is silent on what happens when only entry_id is supplied with no changes, and on shelf_id, leaving two meaningful gaps for a zero-required-parameter tool.

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?

With 15 parameters at 67% schema coverage, the description compensates well by naming the mapped parameters (new_title, creator, year, status, rating, notes, dates, fields, private, image_url) and explaining the clearing convention that the schema only repeats for some fields. shelf_id is left undocumented in both places, and the all-optional schema's minimum-call requirement is unaddressed.

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 and resource ("Change one entry on their shelves") and enumerates the editable attributes, so it is clearly distinct from edit_shelf (shelf metadata) and add_to_shelf. It does not, however, distinguish itself from overlapping siblings such as update_rating, update_status, update_notes, set_dates, or clear_rating, which touch the same fields on the same object.

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 concrete identification guidance: use entry_id, or fall back to title plus shelf when a title is ambiguous across two shelves. That is real when-to-use-this-shape guidance, but there is no guidance on when to choose this tool over the narrower single-field siblings.

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