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

Annotations already declare idempotentHint=true, destructiveHint=true, and openWorldHint=false, so the safety profile is largely structured. The description still adds real value beyond that: it discloses partial-update semantics via updateFields and the version-mismatch recovery behavior. It stops short of stating permissions or exactly what 'destructive' means here, hence not a 5.

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?

Front-loaded with the core action, then scoping, then the concurrency workflow and failure branch. Every clause carries distinct, actionable information with no filler.

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 full annotation coverage, 100% schema coverage, and no output schema, the description supplies the missing operational context: the partial-update contract, the item-safety guarantee, and the version-conflict recovery procedure. Nothing needed to invoke it correctly is missing.

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% and the schema already documents updates, updateFields (including the empty-string clear convention), listId, and expectedVersion in detail. The description's parameter content (field list, updateFields scoping, listId/expectedVersion sources) largely restates the schema, so the 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 ('Change one owned Library List's own details') and enumerates the affected fields. It explicitly distinguishes itself from item operations ('never touches the list's items') and from trip checklists, so an agent can separate it from library_list_item_update and checklist_item_update without opening any 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 precondition for the required optimistic-concurrency args ('Use the listId and expectedVersion from the latest library_list_get'), an explicit error-recovery path ('On library_version_mismatch, read the list again...never retry blindly'), and a scope exclusion ('Library Lists only, not trip checklists'). When-to-use, when-to-recover, and when-not-to-use are all covered.

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