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

readOnlyHint=true already tells the agent this is a safe read, so the description's added value is the bucketed-series semantics ('bucketed by interval') and the underlying endpoint mapping. It does not mention rate limits, whether metrics are pre-aggregated vs computed live, or latency, so it adds modest context beyond the annotation.

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 front-loaded sentence with no filler; the bucketing constraint and metric list come before the endpoint note. Every clause carries information.

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 partially compensates by naming the returned metrics and the bucket dimension, but it still leaves the series/response shape (e.g., per-bucket records, total vs. per-interval values) unexplained. It could say more about the return payload, but the metric enumeration covers the essentials.

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%, so start_date/end_date/interval/product_id/customer_id/organization_id are already documented in the schema. The description only restates the date-range and interval concepts without adding format or filter semantics beyond that baseline.

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?

Specific verb (Fetch) + resource (revenue and subscription metrics) with the dimensions named (orders, revenue, MRR, active subscriptions) and the bucketing scope. It is clearly distinguishable from sibling list_* tools and the single get_meter_quantities tool.

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?

The description states the data shape but never says when to choose this over alternatives such as polar_list_orders/list_subscriptions for raw records or polar_get_meter_quantities for usage. No prerequisites, no exclusions, no routing guidance.

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