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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered; the description goes further by disclosing the computation method (circular pool and conversion math solved with fractions, then rounded to whole shares) and by stating the 'Illustrative only; not legal or tax advice' caveat. The return enumeration (price per share, cap/discount/conversion price, shares issued, fully diluted %) is useful context but is partly redundant with the output schema, keeping this just short of a 5.

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 trigger condition is front-loaded and each subsequent sentence earns its place: outputs, computation approach, then limitations. It is dense and slightly long, and the detailed list of return fields duplicates the output schema, which is the main efficiency loss.

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 9-parameter modelling tool with heavy domain complexity, the description covers what triggers it, what it computes, how it handles the hard math (circular pool, fractional conversion), what it returns, and what it explicitly does not model. With an output schema present and annotations covering safety, nothing an agent needs in order to call it correctly is missing.

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 the schema already explains every parameter in detail, and the baseline is 3. The description adds some semantic grounding by defining what the outputs mean conceptually (cap price, discount price, conversion price being the lower) and by calling out the pre-money pool top-up, but it does not explain individual parameters such as shortcut duplicates (new_money, pre_money_valuation, target_pool_percent) beyond what the schema states.

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 opening sentence names a specific verb and resource ('cap table calculator or startup dilution calculator') and enumerates the exact scope: pro-forma cap table before/after post-money or pre-money SAFEs, convertible notes and/or a priced round. An agent can distinguish this from the sibling calculate_safe_ownership, which by name covers only SAFE ownership, without opening either schema.

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?

"Use this when the user wants..." gives an explicit trigger condition, and the closing sentence carves out clear exclusions (no liquidation preferences, vesting, anti-dilution, or more than one priced round). It does not name or route to the sibling calculate_safe_ownership as an alternative, which is the one missing piece for a 5.

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