fs_stat

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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description discloses a non-obvious behavioral side effect: the VM remains locked by this session and requires an explicit vm_unlock call. This is valuable information an agent would not otherwise know from the schema or 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?

Two short sentences, both earning their place: the first states the core operation, and the second warns about the lock lifecycle. No filler or redundancy.

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?

The description covers the core purpose, the critical lock/unlock requirement, and the read-only nature of the operation. Since there is no output schema, it does not describe the exact shape of returned metadata, which is a minor gap, but the tool can still be correctly selected and invoked.

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 describes vm_name but leaves path as a bare string. The description adds meaning by clarifying that path is a guest filesystem path, helping distinguish guest paths from host paths. With 50% schema coverage, this partial compensation is meaningful, though vm_name semantics are already covered by the schema.

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: 'Read metadata for a guest filesystem path.' This clearly distinguishes fs_stat from sibling tools like fs_list, fs_move, and fs_drives, which perform different operations on the filesystem.

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 implied usage context by stating what it reads, and it provides an important follow-up instruction: 'call vm_unlock when finished.' However, it does not explicitly compare against alternatives or state when to choose this tool over other fs_* tools, so the guidance is only partially complete.

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