List Compute Instances

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

No annotations are provided, so the description carries the burden. It communicates a read-only 'List' behavior and the project/zone scope, which is useful. However, it does not disclose pagination behavior, authentication needs, or what fields the returned instances contain, leaving some behavioral detail implicit.

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 a single well-structured sentence, front-loaded with the action and resource. It contains no filler, repetition, or irrelevant details.

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 zero-required-parameter read tool with fully documented optional parameters, the description plus schema is mostly sufficient. However, there is no output schema and the description does not explain what is actually returned, pagination behavior, or how the 'project' is determined, leaving some contextual gaps for an agent.

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 schema already provides 100% coverage of all three parameters, so the baseline is 3. The description adds extra semantic value by clarifying that omitting zone means listing across the entire project, while including a zone restricts the listing to that zone. Filter and pageSize semantics remain adequately handled by the 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 uses a specific verb ('List'), names the exact resource ('Compute Engine VM instances'), and gives the scope ('across the project or within a zone'). This clearly sets it apart from mutation/status siblings like gcp-compute-delete-instance and get-compute-vm-status.

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 gives no explicit guidance on when to use this tool versus alternatives. It does not mention that it is the read-only listing counterpart to create/start/stop/delete, nor when a user should instead use get-compute-vm-status. The only usage signal is implied by the name and purpose.

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