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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavioral context – that data is realtime and bounded to a 30-minute window – which is the defining trait of this endpoint versus a standard report, though it omits things like data latency, sampling, or rate limits.

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?

Single well-formed sentence with the resource and its scope front-loaded; no filler, no restatement of the name.

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 no-required-param, output-schema-less reporting tool, the description conveys what the call returns (active users broken down by a chosen dimension) and the recency window. It is reasonably complete, with only minor gaps around return format and the relationship to sibling GA4 tools.

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 100% and each parameter (limit, filter, metrics, minutes, dimensions, property_id) is documented with defaults and examples, so the schema carries the load. The description's mention of country/page/traffic-source/device breakdowns loosely echoes the dimensions parameter but adds no syntax or format detail beyond the schema.

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+resource (realtime active users in GA4) plus the exact scope: a 30-minute window broken down by country, page, traffic source or device. An agent can immediately distinguish this from the historical ga4_run_report sibling.

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?

The realtime framing implicitly tells the agent this is for 'right now' monitoring versus historical reporting, but it never names ga4_run_report or ga4_list_properties as alternatives, nor states when-not to use it. Usage is inferable but not spelled out.

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