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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered; the description adds real context beyond that: the 500-row hard cap, the warning that the row sum is NOT the overall total, and that the time window includes today. It does not mention sampling, data lag, or continuity/attribution thresholds, which is why it is not a 5.

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?

Very dense for three sentences: resource, time window, row-limit caveat and workspace note are all front-loaded with no filler. The em-dash-clause structure is slightly telegraphic and mixes German prose into English tooling, 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 values need no explanation, and the description covers the aggregation caveat and the workspace scoping that an agent would otherwise get wrong. The only gap is the absence of stated defaults and any note on data freshness or row ordering.

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 0%, so the description carries the burden and does so for all three parameters: days is the last N days including today, limit is a row cap of at most 500, and workspace is a customer slug that is optional when only one workspace exists. It omits the actual defaults (7 and 50) and value types, which keeps it below a 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 the exact resource (Traffic-Quellen), the dimensions used (sessionSource/sessionMedium) and the metrics returned (sessions, newUsers, engagedSessions). This distinguishes it immediately from ga4_top_pages, ga4_conversions and the generic ga4_report without needing to open any 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?

Explicitly routes the agent to ga4_report with dimensions=[] when totals rather than per-source rows are needed, which is the main selection decision for this tool. It does not, however, contrast itself with nearby siblings such as ga4_top_pages or ga4_conversions, so the guidance is clear but not exhaustive.

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