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

Annotations already declare write/destructive/openWorld=false, and the description adds genuine behavior beyond them: 'Parts left out stay as they were' documents merge semantics of the overwrite, and 'Free.' discloses that the call costs nothing. It does not explain what an empty `event` resets, permissions needed, or the response, but the annotation coverage lowers that burden.

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?

The purpose is front-loaded in the first clause, and every later sentence maps to a parameter or a calling decision. It is dense and a bit clause-heavy, but no sentence 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 4-parameter, no-output-schema configuration tool, the description covers meaning, partial-update behavior, and cost. The main remaining gap is return/confirmation behavior and what happens to the users report after a change.

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 must carry the full semantic load, and it mostly does: `event` is explained as a server-side event name sent to /t/u with empty meaning any product action, `withinDays` is anchored to signup, `minCount` to repetition, and `minValueCents` to value gating (0 vs >0). It does not state defaults for fields omitted on a first-time set, leaving some ambiguity.

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 opens with a concrete verb+resource framing: it sets 'the rule that counts a new user as activated' and ties it to 'the users report', so an agent can tell it configures an activation criterion rather than a goal, funnel, or listing. It does not name or contrast any sibling tool by name, so sibling differentiation is inferred rather than stated.

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?

It gives real selection guidance for the key decision ('Pick the one action that means they got what they came for, from the code; for a product paid by use, the action that costs money'), plus the partial-update rule that omitted parts stay unchanged. There are no explicit when-not-to-use conditions or named alternatives (e.g., goals_save).

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