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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and non-open-world, so the safety profile is fully covered. The description's contribution is scoping the payload to aggregate performance results rather than raw run data; it says nothing about permissions, data freshness, or aggregation semantics.

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?

One compact sentence with the metric list front-loaded and zero filler. It is a noun-phrase fragment rather than a full statement of action, which is a minor structural weakness but not wasteful.

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 no output schema, the description usefully enumerates the metric families returned, which is exactly the gap it needs to fill. Missing usage routing is a modest gap for a read-only reporting tool whose annotations already convey safety.

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%, with days ('30, 90 or "all"'), touch enum, and the journeyId cross-reference to list_journeys all documented in the schema. The description adds no syntax or format detail beyond that, so the baseline 3 applies.

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?

Names the resource (a journey) and enumerates the specific metrics returned — entries, email opens/clicks, goal conversions, split test paths — which distinguishes it from config-oriented siblings like get_journey and run-oriented ones like get_journey_run. It lacks an explicit verb, but the content scope makes the purpose unambiguous.

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?

There is no statement of when to reach for this tool versus get_journey, get_journey_run, or list_journey_runs, nor any prerequisite or exclusion. 'Over a period' hints at a reporting context but leaves the agent to infer selection on its own.

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