fs_stat

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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true. The description adds a non-obvious behavioral detail: 'VM remains locked by this session; call vm_unlock when finished.' This goes beyond annotations by informing the agent of a side effect (session lock) and a required follow-up action. There is no contradiction with 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?

The description is two short sentences. The first is action-focused and front-loaded. The second provides an important behavioral caveat. Every word earns its place, with no repetition or 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 single-parameter, read-only tool with no output schema, the description is nearly complete. It states the operation, clarifies the parameter's meaning, and discloses the locking side effect. The only gap is not describing the return metadata (e.g., what fields are included), but this is somewhat inferable from the tool name 'stat'. The lock/unlock context adds critical operational completeness.

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 only parameter 'path' has 0% schema description coverage. The description clarifies that the path is a 'guest filesystem path', which adds meaning beyond the raw schema field. However, it does not elaborate on path format, absolute vs relative, or expected behavior for missing paths. This is minimal compensation for the coverage gap, but not rich enough to warrant a 4.

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 a specific action ('Read metadata') on a specific resource ('guest filesystem path'). This distinguishes it from sibling tools like fs_list (which lists directory contents) and fs_mkdir/fs_move/fs_delete (which mutate the filesystem). The scope is precise and unambiguous.

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 provides no explicit when-to-use guidance or alternatives. It does not mention that fs_list would be used for listing entries or that other fs_* siblings are for mutations. The locking note ('call vm_unlock when finished') is about post-operation session management, not tool selection, so it does not help an agent choose between this and similar tools.

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