add_disk_to_vps

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

Annotations already indicate this is a mutating (non-read-only), non-idempotent operation. The description adds meaningful behavioral context by highlighting the monetary consequence and the mandatory confirm flag. This exceeds annotation coverage without contradicting it.

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 compact sentences with the primary action, the critical behavioral warning, and the alternative routing. Every clause adds value and the most important information is front-loaded.

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 straightforward disk-addition tool with three parameters and no output schema, the description covers all key agent decisions: action, financial warning, confirmation flow, and sibling differentiation. It doesn't mention edge cases like existing disk size limits, but those would presumably be validated at runtime; the core invocation guidance is 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?

With 0% schema description coverage, the description properly compensates: it clarifies size is in GB, that vps_id refers to the target VPS ('directly to this VPS'), and that confirm must be true. Each parameter is given practical meaning beyond the raw 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 states a specific action ('Add a new disk') and resource ('to this VPS') with the size in GB. It also distinguishes itself from the sibling purchase_volume by explicitly naming what it is not, making the tool's purpose 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?

It clearly directs the agent to purchase_volume when a standalone, independently-manageable volume is needed instead. It also instructs that the confirm=true parameter is required because the operation spends real money, giving explicit usage conditions.

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