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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered structurally. The description adds the outcome state (item becomes unrated rather than deleted), which is genuinely new information beyond the annotations. It stops short of mentioning error behavior for already-unrated items, but given idempotentHint that gap is minor.

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 short sentences, zero filler, with the purpose front-loaded and the sibling relationship appended as a routing hint. Nothing could be trimmed without losing meaning.

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 simple one-target mutation with full schema coverage and rich annotations, the description supplies purpose, outcome, and sibling routing. Only edge-case behavior (target missing, already unrated) is absent, which is a minor gap rather than a blocker.

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 description coverage is 100%, with media_type enumerated and item_id explicitly preferred over title. The description adds no parameter-level guidance beyond what the schema already states, so baseline 3 applies.

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 ('Remove the user rating from one library item') plus the resulting state ('leaving it unrated'). It also explicitly contrasts with the update_rating sibling, so an agent can distinguish the two without consulting 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?

'The undo for update_rating' gives a concrete selection rule: use this when the user wants to unrate rather than set a new value. It does not spell out exclusions (e.g., item not found, or whether an unrated item errors), but the intended usage is clear.

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