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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the 30-day maximum range, single-container scope, and 'in one call' aggregation promise. It stops short of describing result shape, but an output schema exists to carry that.

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?

Two sentences, front-loaded with what you get before the routing alternatives. The first sentence is a dense enumerated list but each item carries information; nothing is padding. Slightly run-on, which keeps it from a 5.

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?

Covers return contents, scope limits, the routing decision against both relevant siblings, and safety behavior is carried by annotations plus an output schema. An agent has everything needed to call this correctly and to pick it over alternatives.

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 the baseline is 3. The description goes slightly beyond the schema by imposing the ≤30-day cap on date_from/date_to, which the schema itself does not state. It does not explain currency, attribution, or server_name, but those are documented in 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 exactly what is returned (event totals, consent stats, recovery stats, per-source breakdown) with a concrete scope (one container, one date range of at most 30 days). It explicitly distinguishes itself from run_report and get_report by naming the report types each covers, so an agent can select without opening 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?

Gives explicit routing: sessions/channels/landing pages/goals/period comparison/longer ranges go to run_report, and event-name/day/hour/device/browser breakdowns go to get_report. It also states the selection constraint (single container, ≤30-day range) that governs when this tool applies.

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