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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context beyond them: substring vs exact filter semantics enforced by the API, that empty clusters are still returned (count 0), that clusters do NOT narrow placement, and that an absent 'virtualization' field means unknown capability. That is real behavioral disclosure an agent could not infer from structured fields.

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?

Front-loads the core purpose and filter semantics, then moves to secondary details (constraints, virtualization, empty clusters) in separate paragraphs. The tag-placement paragraph is long but each sentence carries distinct operational meaning; the only mild cost is overall length.

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?

With no output schema and six optional parameters, the description compensates well: it enumerates the returned fields (provider, state, constraints.tags, constraints.allow.pool, virtualization) and explains the edge case of empty clusters. An agent has everything needed to call and interpret this tool correctly.

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%, so the baseline is 3, but the description adds genuine meaning: hostname and nickname are case-insensitive substring matches (a partial hostname suffices) while cluster and state are exact filters applied by the API. It also clarifies that a Cycle cluster does not itself restrict placement, which changes how an agent should interpret the cluster parameter.

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?

Opens with a specific verb+resource+scope: 'List the physical/virtual servers making up your Cycle infrastructure, grouped by cluster.' That distinguishes it cleanly from siblings like list_containers, list_virtual_machines, and list_environments, and the follow-up sentence states exactly what each entry reveals (hardware, cluster, provider, state).

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 clear usage context ('Use to see what hardware exists, which cluster it belongs to, and its provider and state') and a concrete workflow trigger — read tags here to confirm a tag exists before referencing it in a container constraint. It cross-references deploy_application and deploy_virtual_machine but never states when NOT to use this tool versus a sibling lister.

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