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

Annotations already mark this as readOnlyHint=true, and the description adds meaningful behavioral detail beyond that: it discloses the empty-list response with setup instructions when no vault is synced. It also states the type of information returned, which is useful for agents anticipating the tool's output.

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: what the tool returns, when it should be called, and the edge case of no synced vaults. The description is front-loaded with the core action and return value, and contains 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 parameterless read-only tool with no output schema, the description is fully sufficient: it explains the tool's scope, the returned fields, the intended invocation timing, and the behavior in the empty case. Nothing needed to call 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?

The tool has zero parameters and schema description coverage is 100%, so the baseline is 4. There is no parameter ambiguity, and the description correctly focuses on behavior rather than inventing parameter details that do not exist.

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 begins with a specific verb and resource: 'List the Obsidian vaults the user has synced into their Second Brain.' It also enumerates the returned data (note counts, folders, tags, last sync), which clearly distinguishes this vault-level tool from sibling tools that operate on notes or messages.

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 explicit guidance: 'Call this before answering anything about their Obsidian setup' and lists concrete situations such as checking whether a vault is connected or what it contains. It stops short of naming sibling alternatives like list_obsidian_notes or search_obsidian_notes, so the contrast with alternatives is implied rather than explicit.

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