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

Beyond the annotations (not read-only, not destructive, idempotent), it discloses partial-update semantics, the optimistic-concurrency requirement, and the OUT_OF_SYNC rejection with 'nothing is written'. This adds crucial behavioral context not present in structured annotations.

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?

Three sentences, each earning its place: purpose, patch behavior, and the required concurrency token. No filler, and the most important constraint (baseUpdatedAt) is emphasized clearly.

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?

Given the empty input schema, the description covers the core requirements (id, baseUpdatedAt, partial patch) and the error behavior. It is slightly incomplete in that it does not specify the exact parameter names for id and patchable fields, which an agent would need for a flawless call.

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 input schema is empty, so the description carries the parameter burden. It names baseUpdatedAt and refers to id, and clarifies that only supplied fields change. However, it does not enumerate the exact id parameter key or allowed field names, leaving some ambiguity for invocation.

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 clearly states a specific verb ('patch'), resource ('existing user-authored item'), and scope ('by id'). It is distinct from vault_create_item and other vault_update_* siblings by naming the resource type explicitly.

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?

It explicitly instructs to confirm the id via vault_search_items / vault_get_item before updating, and requires baseUpdatedAt from a fresh read. This provides clear preconditions and directs the agent to sibling read tools for correct usage.

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