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

Adds real behavioral context beyond the annotations: it discloses the dry-run default ('Previews unless confirm is true') and reassures 'Never deletes'. The preview semantics are the key operational trait and are stated plainly, though it doesn't mention auth requirements or rate limits — annotations already cover the safety/hint profile.

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 tight sentences with zero filler, front-loading the core action before the preview caveat and the non-destructive reassurance. Every clause earns its place.

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 mutating tool with no output schema, the description covers the essentials: what it does, the safe preview default, and that it's non-destructive. It falls slightly short on counting_method semantics and on pointing to the read counterpart for verification.

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 only 50%, and the description meaningfully compensates for confirm by explaining its preview behavior. But counting_method (an enum with a default) is never explained — ONCE_PER_EVENT vs ONCE_PER_SESSION semantics remain undocumented in both places, leaving a 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?

States a specific verb and resource ('Mark an event as a key event (conversion) on a client's GA4 property') and distinguishes itself from the read-side sibling ga4_list_key_events. Concrete examples (generate_lead, phone_click) anchor the concept immediately.

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?

Usage is implied through the lead-generation framing and the example event names, giving the agent a sense of when this applies. However, it never names the alternative (e.g. ga4_list_key_events to inspect existing ones) or states when NOT to create one, so routing guidance is only moderate.

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