fs_mkdir

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

The description discloses an important non-obvious side effect: the VM remains locked by this session and the caller must call vm_unlock when finished. This goes beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false) and gives the agent critical behavioral context. No contradiction with annotations exists.

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 with the primary action front-loaded and the lock/unlock obligation placed immediately after. Every sentence contributes useful information with no redundancy or restatement of the tool name.

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 simple mkdir operation, the description covers the essential action and the critical lock/unlock contract. However, with no output schema and low parameter coverage, it leaves return behavior, error cases, and the effect of recursive creating to inference. It is adequate but not 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?

Schema description coverage is only 33%, with only vm_name described in the schema. The phrase 'guest directory' hints that path refers to a filesystem path inside the guest, but the recursive boolean and path semantics are not meaningfully explained. Since coverage is low, the description needed to compensate more than it does.

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 object, 'Create a guest directory,' which clearly identifies the operation and target. It does not name or compare against sibling filesystem tools like fs_move or fs_delete, so it stops short of full differentiation, but the purpose is 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?

There is no guidance on when to use fs_mkdir instead of related tools such as directory_push, fs_move, or fs_delete. The only additional context is about the VM lock, which is a postcondition rather than a selection criterion for choosing this tool.

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