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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered structurally. The description's only added behavioral detail is the return payload (ROI %, profit, multiple), which duplicates the existing output schema rather than adding new context.

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?

Four compact sentences, front-loaded with the core purpose and then inputs/outputs/cross-reference. Slightly redundant to restate return values that the output schema already provides, but nothing is padded.

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?

For a simple two-parameter calculator with an output schema, the description covers purpose, inputs, and related-tool routing adequately. The only gap is the absence of guidance on units or interpretation, which is minor given the annotations and output schema.

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 only two parameters, so the schema already documents 'investment' and 'return_value' fully. The description merely restates them as 'investment cost' and 'return value' without adding units, edge-case handling, or sign conventions.

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 ('Compute Return on Investment as a percentage') and enumerates the intended use cases (investments, marketing spend, projects). It is clearly distinct from most siblings, though it never explicitly distinguishes itself from close cousins like calculate_solar_roi or calculate_rental_yield.

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 clear context for when to use it ('evaluate investments, marketing spend, or projects') and points to list_bundles for related finance calculators. It offers no explicit when-not-to-use or alternative-tool routing.

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