list_active_sessions

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

Annotations cover read-only/idempotent/non-destructive, and the description goes well beyond them: it discloses the required Sessions privilege, the graceful-degradation behavior for low-privilege accounts (single explanatory row instead of a traceback), and the default folding of vCenter solution users into service_sessions. That is exactly the privileged-operations context an agent needs.

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 core purpose, then return fields, then usage guidance. The row-field enumeration (user_name, full_name, login_time, ...) is dense but earns its place given there is no output schema. Slightly long, but no filler sentences.

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, the description compensates by enumerating the row fields and the envelope's total, plus the current flag and service-session folding. Permissions, targeting and the read-only boundary are all covered, so nothing an agent needs to invoke this correctly is missing.

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 real semantic value for include_service by explaining that solution users are folded by default and surfaced in the service_sessions count. It does not add anything for limit or target, but the default-behavior clarification lifts it above baseline.

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 and resource: 'Currently authenticated vCenter/ESXi sessions (who is logged in).' The scope is unambiguous and it is clearly distinguishable from sibling monitoring tools like list_all_clusters, and it explicitly names list_active_tasks as a related-but-different tool.

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 an explicit purpose statement ('Use this to attribute a change to a person'), names the complementary sibling (list_active_tasks, which names the user who started each task), and states a boundary ('terminating a session is not supported here'). When-to-use and when-not-to-use are both covered.

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