get_datastore_capacity

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial non-obvious behavior: point-in-time semantics, that provisioned_gb is aggregated by the endpoint over registered VMs so vCenter and direct ESXi diverge, that vm_count delimits the figure's coverage, and that vms_not_connected uses None as 'could not be read'. This is exactly the extra context annotations cannot carry.

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-loaded with the tag, one-line summary, then the returned envelope and the risk rationale; the 'whose figure' paragraph is dense but every clause resolves a real ambiguity about divergent per-endpoint numbers. Slightly long and could be tightened, but nothing is filler.

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 read-only list tool with no output schema, the description supplies the return fields, the risk interpretation, the point-in-time caveat and the multi-endpoint aggregation caveat — everything an agent needs to call it and correctly interpret results.

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 description coverage is 100% and the two parameters (limit, target) are already documented in the schema. The description adds no argument syntax or format detail beyond the schema, so the baseline 3 for full-coverage schemas applies.

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?

States a specific verb and resource ('per-datastore capacity') plus the distinctive capability (thin-provisioning over-commit) and explicitly contrasts itself with list_all_datastores, which it says 'lacks' the risk signal list. An agent can distinguish it from the 30+ siblings without opening a schema.

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 explicit routing: 'Use this for the capacity view, then investigate_datastore to drill into a specific datastore's hosts, VMs and alarms.' It also draws an out-of-scope boundary by handing remediation ('delete snapshots, storage vMotion') to another agent (vmware-aiops), which tells the agent when not to act here.

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