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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutation risk is known; the description still adds real value beyond that by disclosing the two-phase preview-then-confirm protocol and the requirement for explicit user consent. It does not state whether unmarking restores prior state or what the preview contains, leaving minor behavioral gaps.

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, zero waste, with the operation stated first and the confirmation protocol immediately after. Every clause carries information an agent needs.

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 destructive 6-parameter mutation with no output schema, the description covers the highest-risk aspect (irreversible-looking change gated by confirm) and specifies the preview behavior. The remaining omissions (folder, language, and default property selection) are modest but real for an agent assembling a first call.

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 50%, and the description explains the meaning of action (mark vs unmark) and the confirm gate, which are the two most consequential parameters. It says nothing about folder, language, or how the property parameter is resolved when omitted, so it only partially compensates for the coverage gap.

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 a specific verb pair (mark/unmark) and resource (a GA4 event as key event/conversion) scoped to the selected GA4 property, which clearly separates it from the read-only sibling ga4_key_events. It stops short of explicitly naming that sibling as the alternative, so it is clear but not fully differentiated.

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 concrete invocation guidance: the first call is a preview, and the change is applied only on a second call with confirm=true after the user explicitly agrees in chat. That is a strong when/how rule, though it does not say when to use ga4_key_events to inspect existing key events instead.

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