internal_rate_of_return

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

The description discloses the numerical method (Newton's method + bisection fallback) and the prerequisite sign pattern, which is useful. However, it does not cover failure modes like multiple IRRs or non-convergence, and there are no annotations to provide additional safety/permission 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?

The description is concise and well-structured: definition, algorithm note, requirement, and argument list. Every sentence serves a purpose, with no redundancy.

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?

Given that an output schema exists, return values need no explanation. The description covers the mathematical definition, algorithm, prerequisite, and parameter details. It lacks discussion of edge cases (e.g., multiple IRRs), but is otherwise adequate for a straightforward calculator.

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 0%, but the description compensates thoroughly. It explains cashflows with a concrete example and defines guess as a decimal starting rate for Newton's method, giving both format and purpose.

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 explicitly defines 'the per-period rate where NPV == 0', which is a clear and specific statement of the tool's purpose. This distinguishes it from sibling tools like net_present_value, which calculates NPV rather than the rate.

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 the tool is for calculating IRR but does not explicitly state when to use it over alternatives. It mentions a constraint (at least one negative and one positive cashflow) but lacks scenario-based guidance or exclusions.

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