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

Annotations already declare readOnlyHint=false and destructiveHint=true, and the description adds context about purchasing add-ons. However, it does not disclose impact on billing, reversibility, or any additional behavioral traits beyond what annotations convey. It also introduces an inconsistency by mentioning 'firewalling' which is absent from the schema.

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 relatively concise with one main sentence and a constraint. Some filler like 'In order to' could be trimmed, but overall it is suitably brief and front-loaded with the key action.

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 mutating operation with 4 parameters, no output schema, and a nested body, the description is incomplete. It lacks behavior details, return value expectations, prerequisites, and fails to mention that the schema only supports backup and privateNetworking. The mention of firewalling is a notable omission/inaccuracy that harms 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 description provides no parameter information and actually conflicts with the schema. It states 'firewalling and private network addon is allowed' but the input schema only contains 'backup' and 'privateNetworking' fields. This mismatch could mislead an agent into trying to invoke a non-existent firewall parameter. The description fails to compensate for the 0% schema description coverage.

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 identifies the action as upgrading instance capabilities by purchasing add-ons, and specifies the scope (instance capabilities). It distinguishes from siblings like assignInstancePrivateNetwork, though not explicitly. The mention of 'firewalling and private network addon' narrows the purpose, but the mismatch with schema fields weakens clarity.

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 guidance on when to use this tool versus alternatives such as assignInstancePrivateNetwork or createPrivateNetwork. It implies usage for enhancing instances with add-ons but does not state prerequisites, exclusions, or alternative tools.

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