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

Annotations already establish that this is a read-only, idempotent, non-destructive calculation. The description adds useful context about what results are produced, but does not disclose calculation assumptions, rounding, or edge-case behavior beyond what the annotations and schema imply.

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 compact, front-loads the target user and the three outputs, and avoids unnecessary repetition. The external interactive link is optional and slightly extraneous for tool invocation, keeping it from a full 5.

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 no output schema, the description appropriately explains the three main outputs. It is nearly complete for a calculation tool, though it would benefit from stating key assumptions such as fully diluted ownership treatment or rounding conventions.

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 all four parameters are already documented in detail. The description helps frame what the inputs produce, but it does not add syntax or semantic detail beyond the schema fields themselves.

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 states a clear specific purpose: calculating pro rata check size, post-round ownership, and stake value for an existing investor in a new round. It does not explicitly distinguish this from related sibling tools such as dilution or convertible_note, so it stops short of a 5.

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 gives a clear usage condition: 'For an existing investor in a new round.' However, it does not say when not to use the tool or name alternatives for related calculations like dilution or startup_valuation.

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