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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the read-only nature is covered. The description adds the list of returned fields, which is useful context beyond the annotations, but it does not disclose any additional behavioral traits like error conditions, auth requirements, or return format. Since the annotations carry the safety profile, the description adds moderate value but doesn't go further.

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 description is two concise sentences with no unnecessary words. The core action ('Fetch one item document by id') is front-loaded, and the pairing instruction is useful without redundancy. Every sentence earns its place.

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 one-parameter, read-only getter with an output schema and comprehensive annotations, the description is complete. It tells the agent what the tool does, what fields are included, and how to obtain the id (via vault_search_items). The output schema covers return values, and annotations cover safety, so no further detail is necessary for correct invocation.

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 schema already provides 100% coverage for the single parameter 'id' with a clear description ('Mongo `_id` of the vault document'). The description simply says 'by id', adding no new semantic information beyond what the schema already states. Therefore, the baseline of 3 is appropriate.

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 states a specific verb ('Fetch'), resource ('item document'), and key operation (by id). It lists the included fields (damage info, weight, properties, equip slots, ammo settings), which distinguishes it from other vault_get_* tools, and explicitly names the sibling 'vault_search_items' as the way to locate the id first.

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 description gives an explicit workflow: 'Pair with vault_search_items to locate the id first.' This clearly tells the agent when to use this tool (when an id is available and full item details are needed) and points to the alternative for finding the id. It doesn't explicitly state when not to use it, but the pairing instruction is practical and sufficient for a get-by-id tool.

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