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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the trailing 'Read-only' earns no credit. The description does add useful behavioral context about what the response contains (the metric set and cancellation reasons), but says nothing about currency, currency conversion, timezone/boundary handling, or whether it reflects live vs. cached Stripe data.

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 sentence, front-loaded with the resource and scope, then the enumeration of returned metrics. Nothing is padded, and the trailing 'Read-only' is the only redundancy against the annotations.

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?

No output schema exists, so the description correctly takes on the burden of listing return fields (cancellations, churn rate, MRR lost, reasons), which makes it callable without further reading. Minor gaps remain around currency/aggregation granularity, but for a one-optional-param read tool this is sufficient.

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% and the schema already documents the 1–365 range and the default of 30. The description only says 'over a recent window', which adds no meaning beyond the schema; 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?

States a specific verb+resource ('Subscription churn in the user's Stripe account') and enumerates the exact outputs: cancellations, churn rate, MRR lost, and cancellation reasons. That metric set separates it from siblings like stripe_mrr_summary and stripe_failed_payments without needing to name them.

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 only implied by the subject matter ('churn') and the window framing. There is no explicit statement of when to pick this over stripe_mrr_summary or stripe_failed_payments, and no prerequisites or exclusions are given.

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