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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds value by explicitly listing the returned attributes and noting the required inputs, giving the agent a clear expectation of output without contradicting annotations.

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 well-structured sentences: the first states the purpose and output fields, the second lists required inputs. No redundant filler or unnecessary detail.

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 read-only getter with a comprehensive output schema and full parameter coverage, the description is sufficient. It communicates what the tool returns and what inputs are needed, without needing to explain return values since the output schema exists.

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 100%, with each parameter (project, zone, name) already described. The description only restates that these three inputs are required, adding no deeper semantic meaning beyond the schema. Baseline 3 applies due to high schema 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 states the tool gets basic information about a specific Compute Engine VM instance, enumerating the fields returned (name, ID, status, machine type, creation timestamp, guest accelerators). This distinguishes it from sibling tools targeting other resource types like disks or templates, and from list_instances.

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?

Usage context is implied: it requires project, zone, and instance name to fetch a single instance's basic info. However, the description provides no explicit guidance on when to choose this over alternatives (e.g., list_instances for multiple VMs, or other get_* tools for different resources).

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