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

Annotations already provide readOnlyHint, idempotentHint, and destructiveHint, so the bar is lower. The description adds valuable behavioral context beyond annotations by explaining that MCP keeps no state between calls and that no active vault is persisted, which is essential for agents to understand the tool's actual side effects.

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 compact and front-loaded with the core purpose, then adds only essential usage caveats and an alternative. Every sentence earns its place, and the critical 'does NOT persist' warning is highlighted early.

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 simple single-parameter schema, comprehensive annotations, and presence of an output schema, this description fully covers what an agent needs to know: what it does, what it doesn't do, how to use it, and how it relates to list_vaults.

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 already explains that vault_id can be a name or UUID. The description repeats this concept but does not add new parameter-level meaning beyond what the schema provides, so 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 opens with a specific verb and resource: 'Validate and echo a vault by name or ID.' It clearly differentiates itself from siblings by explicitly stating it does NOT persist an active vault and that it need not be called before read/write operations, unlike what the name 'set_vault' might imply.

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 gives explicit when-not guidance: 'this does NOT persist an active vault' and 'this need not be called first' for read/write tools. It also names the alternative: 'Use list_vaults to see them.' This leaves no ambiguity about when to invoke this tool versus its siblings.

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