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

Annotations already declare destructiveHint=true and idempotentHint=true, so safety is structured. The description goes well beyond them by disclosing that billing continues until the scheduled time, that removal deletes both the machine and its disk, and that spend-capped tokens are restricted to moving removal earlier — consequences not derivable from any structured field.

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, front-loaded with the action and timestamp format, then consequences, then usage rules. No filler; every clause conveys something an agent would otherwise have to guess.

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 destructive, billed, open-world mutation with no output schema, the description covers cost accrual, what gets destroyed, idempotency implications, and the token-permission constraint on direction of change. Nothing material for correct invocation 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?

Schema coverage is 50%: the 'at' parameter is already documented with a date-time format and example, so the description's '(ISO 8601, UTC)' only adds a modest clarification. instance_id is never mentioned in the description, though its meaning is self-evident from the tool's context.

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?

States a specific action and resource — changing when a machine is removed automatically — with the key qualifier 'automatically' that separates it from an immediate termination. Combined with the billing and disk-deletion consequences, an agent can tell this apart from terminate_instance without opening either schema.

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?

Gives explicit when-to-use cases: ending a rental early when the job finishes sooner, or extending a long run. It also names the condition that changes behavior — a token with a spend cap can only move removal earlier — which is exactly the routing rule an agent needs.

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