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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower. The description still adds meaningful context beyond them: results can contain end-user PII, callers should quote minimally and mask identifiers, and sessions are not transferred. It does not cover pagination/cursor behavior, but the PII handling guidance is substantive.

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 sentences, front-loaded with the core action and capability, followed by a compliance note that earns its place. No filler or restatement of the name/title.

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?

An output schema exists so return values need no explanation, and annotations cover safety. But for a 12-parameter tool with low schema coverage, the description omits the semantics of its many filtering knobs, leaving an agent to infer behavior from bare enums.

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 only 42% across 12 parameters, so the description is expected to compensate more. It loosely maps to order_by by naming activity, cost, and failure rate, but says nothing about range, search, cohort_id, minimum_sessions, include_unidentified, order_direction, or limit, leaving most filters undocumented in both places.

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 ('Discover and rank users in a namespace') and scopes it to a namespace, which is more precise than a bare 'list'. It implicitly separates itself from session-fetching siblings via 'without transferring sessions', but never names an alternative tool outright.

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 phrase 'without transferring sessions' implies this is the lightweight path when you don't need session payloads, and ranking options are hinted at. However, there is no explicit when-to-use/when-not-to-use guidance relative to siblings like list_agents, list_sessions, or search.

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