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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds the dual-mode framing, but says nothing about accuracy caveats, rounding, or how omitted optional inputs behave. Some added value over annotations, not much.

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?

The core sentence is dense, front-loaded and earns its place. The trailing promotional URL link is not operationally useful to an agent and slightly dilutes an otherwise efficient definition.

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 an output schema present and full schema descriptions, the agent has everything needed to invoke this correctly; the description only needs to frame scope, which it does. Minor gap: it never states that the mode is selected by supplying winRatePct.

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 every parameter is already documented in the schema, including the currency pattern and the winRatePct 'B2B only, omit for ecommerce' rule. The description adds no parameter-level meaning beyond that; 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 ('Estimate') plus the exact outputs (monthly revenue, ROI, revenue per email, revenue per subscriber) and the resource (an email programme). The named inputs and modes make it trivially distinguishable from near-neighbours like crm_roi_calculator or roas_calculator.

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?

It names the two operating modes (ecommerce vs B2B pipeline), which implies how to configure the call, but gives no explicit when-to-use or when-not-to-use guidance relative to the many sibling ROI calculators. Usage is inferable, not stated.

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