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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds that counts and configuration state come back together, but says nothing about breakdown mechanics (no campaign parameter exists in the schema) or how the two result sets are combined.

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?

A single front-loaded sentence with no padding. The compound 'plus which events are configured as key events' clause is slightly awkward but does carry the dual-return information.

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 read-only reporting tool with 88% schema coverage and no output schema, the description conveys the two things returned (counts and configuration list). Missing is any note on the multi-property requirement or how detail=summary vs full shapes the output, but the schema covers the former.

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 88%, so the schema already documents limit, detail, date_range, start/end date, property, folder and language. The description adds no parameter meaning beyond that, and the one behavior it mentions — 'optional campaign breakdown' — has no corresponding schema parameter, leaving how it is triggered unexplained.

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: shows key events with counts, plus the key-event configuration. That is distinct from the sibling ga4_set_key_event, which mutates configuration, but the description never names that sibling to make the boundary explicit.

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 only implied by the reporting verb and the 'optional campaign breakdown' phrase. There is no statement of when to reach for this versus ga4_overview, ga4_custom_report, or ga4_set_key_event, and no prerequisites such as needing a property selected.

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