Current Active Vault

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

The description explicitly states 'Read-only', which aligns with the readOnlyHint annotation. It adds important behavioral context: the obsidianLiveInstance note clarifies that workspace.* and commands.* tools target a different vault. This goes beyond what annotations provide and fully discloses behavioral traits.

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 a single long sentence with dense information. It is concise and front-loaded, but could be slightly more readable by splitting into two sentences. Still, every part adds value with no waste.

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 tool's simplicity (no parameters), rich annotations (readOnlyHint, idempotentHint), and the presence of an output schema, the description covers everything needed: purpose, output fields, edge cases (no vault configured), and cross-tool behavior (obsidianLiveInstance). It is fully complete.

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 has zero parameters, so the description cannot add parameter-level information. Per guidelines, 0 params baseline is 4. The description does not need to elaborate on parameters.

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 that the tool returns the current vault and the precedence chain explaining why it was picked. It specifies possible values for `reason` (session-selected, env-default, none) and mentions the obsidianLiveInstance note. This is a specific verb+resource that distinguishes from siblings like vault.list or vault.select.

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 implicitly guides when to use: before calling filesystem tools to know which vault they target, and to explain the vault selection to the user. It notes that if reason is 'none', tools will fail until a vault is set. However, it lacks explicit when-not or alternative tool recommendations, which would elevate it to 5.

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