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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds the cohort semantics (signup window combined with event absence), but says nothing about how an unknown or misspelled event name is handled, whether results are capped, or which user fields come back.

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 short sentences, zero padding, with the selection criteria front-loaded ahead of the campaign use case. Nothing is repeated from the schema or annotations.

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?

There is no output schema, so the description should clarify the return shape; it only implies a list of users without stating fields or ordering. For a three-parameter read tool with a fairly self-explanatory title the definition is workable, but an agent still has to guess at event-name validity and result contents.

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 0%, so the description carries the burden. It loosely maps 'last N days' to signed_up_within_days and 'the given event' to event, but never states that event must be a valid event name (list_event_names exists), nor explains the limit parameter or its 1-100 range.

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 names the resource (users) and the precise selection logic: signed up within N days and no recorded instance of a given event, with a concrete example. That distinguishes it from siblings such as find_inactive_accounts and get_recent_signups, though no sibling is named explicitly.

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?

"Good for activation campaigns" gives one positive use case, which is more than nothing. It does not say when to prefer find_inactive_accounts or query_events instead, nor when this tool is a poor choice.

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