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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so safety is covered. The description adds genuinely non-structured context: the returned content (active user count + country breakdown) and the ~30-min freshness window. No auth or rate-limit notes, but the additions exceed the annotation baseline.

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 dense sentence front-loads the tool's identity and output shape, followed by the parameter sourcing hint. Slightly run-on with stacked parentheticals, 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?

An output schema exists, so return-value detail is optional (the description's mention of users + country breakdown is a bonus). With only one required parameter and rich annotations, the description is nearly sufficient; a brief ordering of self vs. ga4_overview/ga4_report would complete it.

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?

With one required parameter and 0% schema description coverage, the description must carry the load, and it does: it tells the agent where to obtain the property (ga4_list_properties) and that a name or number is accepted. It does not name the parameter explicitly, but the syntax clarity is a real improvement over the bare 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 and result ('number of users currently active on the site + a country breakdown'), with an explicit freshness window (last ~30 min). The 'realtime' scoping cleanly separates it from historical GA4 siblings like ga4_overview and ga4_report.

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 by the 'realtime' framing and the ~30-min window, but there is no explicit when-to-use / when-not guidance versus ga4_overview, ga4_report, or other GA4 tools. The pointer to ga4_list_properties is a sourcing hint rather than a selection rule.

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