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

Annotations already declare readOnlyHint=true and idempotentHint=true, indicating a safe, pure calculation. The description adds the exact mathematical formula, which clarifies the computation's deterministic nature and the relationship between inputs. This goes beyond the annotations without contradicting them.

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 description is a single, front-loaded sentence that includes the tool's purpose and the formula. Every word earns its place; nothing is redundant or excessive.

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 two-parameter, read-only calculator with a clear formula and an output schema, the description is complete. It explains the exact computation, and annotations cover safety and idempotency. No further behavioral details are necessary.

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% with descriptions for both parameters, so the baseline is 3. The description adds value by explicitly showing how the two rates (nominalRatePct and inflationRatePct) are used in the Fisher equation, providing mathematical context beyond the schema's simple 'in percent' descriptions.

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?

The description clearly identifies the tool's purpose: computing the real (inflation-adjusted) return from a nominal rate. It includes the specific Fisher relation formula, which precisely distinguishes it from general inflation adjustment tools like 'inflation-adjust' and return-related siblings.

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 implies usage context (converting nominal to real return) but does not explicitly state when to use this tool over alternatives like 'inflation-adjust' or 'required-return'. No exclusions or alternative recommendations are provided, so the guidance is implied rather than explicit.

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