List VPCs in a region

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

Beyond the readOnlyHint and idempotentHint annotations, the description discloses key runtime behavior: the backend currently only populates ccx_num_vpcs/ccx_vpc_ids, may return zero even when VPCs exist, and empty results should be interpreted as 'unknown' rather than 'none'. It also states the auth requirement.

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 short sentences front-load the purpose, then add the auth prerequisite and the critical empty-result caveat. No sentence is wasted.

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 single-parameter, read-only tool with no output schema, the description covers invocation requirements, current backend limitations, and interpretation of results. It is sufficient for an agent to call and correctly interpret the response.

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% and the single region parameter is already described in the input schema. The description only reiterates that this is for an AWS region and adds no new parameter-format or value constraints.

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 opens with a specific verb and resource: 'List VPC ids known to CCX for an AWS region'. It also scopes the operation by region and distinguishes it from sibling list tools for datastores, nodes, and users.

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 clearly implies this is the VPC-list operation among the sibling admin tools, and adds the prerequisite that basic auth credentials are required. It does not explicitly name alternatives or state when not to use it, but the resource-specific scope makes the usage context clear.

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