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

Beyond the annotations, the 'BEHAVIOUR' section states it is a pure deterministic calculation with no side effects, network, or storage access, and idempotent/non-destructive. It also discloses the edge case: returns 0 when there is no invested capital. This adds value beyond the readOnlyHint and idempotentHint annotations.

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 well-structured with labeled sections, front-loaded with the core purpose. Although longer than many tool descriptions, every sentence adds useful operational guidance — usage conditions, behavior, return format, and parameter semantics — with no filler or redundant restatement.

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 single-parameter calculation tool with fully annotated safety hints, the description covers everything needed to invoke it correctly: formula, input semantics, edge case, return shape, and differentiation from siblings. The absence of an output schema is compensated by the explicit RETURNS section describing { moic, cash_flows }.

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% for the single cash_flows parameter, so the baseline is 3. The description adds the computational formula (sum of positive cash flows divided by sum of absolute negative cash flows) and clarifies the ordered nature starting at time 0, which is more explicit than the schema. It mostly reinforces the schema but adds the formula and edge-case behavior.

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 opens with a specific verb and resource: 'Calculate the Multiple on Invested Capital (MOIC): total distributions divided by total invested, with no discounting and no time value.' It clearly defines what the tool computes and the key formula, distinguishing it from financial metrics like IRR and NPV by stating it ignores time value.

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 explicitly provides 'WHEN TO USE' and 'WHEN NOT TO USE' sections, naming the alternative tools (calculate_irr, calculate_npv) and the exact conditions that should route an agent to them. This leaves no ambiguity about when the tool is appropriate.

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