GA4: Available dimensions & metrics

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

Annotations already cover safety (readOnlyHint=true, openWorldHint=true), so the bar is lower. The description still adds genuine behavioral detail about the response shape: unfiltered calls return only apiNames, while search/category/customOnly calls additionally return uiName, category and metric type — a meaningful disclosure not derivable from annotations.

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?

Three dense sentences, front-loaded with purpose then usage then output behavior; no filler. The compression ('incl.', 'customEvent:…') makes it slightly harder to parse than a cleanly structured alternative, but nothing is wasted.

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?

With six parameters and no output schema, the description carries the burden of explaining returns and largely does so by distinguishing the filtered and unfiltered output shapes. Combined with the fully documented schema, an agent has enough to call this correctly and interpret the result.

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 100%, so baseline would be 3, but the description adds real meaning beyond the schema: it specifies that search matches substrings in apiName, uiName and description, and that it conditions which output fields appear. The 'details' parameter is not addressed in the description, keeping it below 5.

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 ('Lists the dimensions and metrics that ga4_run_report knows for this property') and explicitly scopes it to the property, including custom ones with their naming prefixes (customEvent:…, customUser:…). An agent can tell this apart from report-running siblings like ga4_run_report or ga4_run_funnel_report without opening a schema.

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?

Gives a clear precondition: 'Use before a report instead of guessing API names,' which explicitly routes the agent away from trial-and-error on ga4_run_report. It lacks any 'when not' guidance or differentiation from the closely related ga4_list_custom_definitions sibling, so it falls short of a 5.

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