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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuine context beyond that: it ties the math to a specific source URL and warns that the ARR multiple is a heuristic, not a valuation, and the output is illustrative rather than legal advice.

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?

Four sentences, all of which earn their place, with the core action front-loaded before the sourcing and caveat sentences. Dense but not padded.

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 9 optional parameters and no output schema, the description explains the inputs conceptually but never states what the tool returns (equity percentages, advisor grant dilution, the multiple). It is adequate but leaves the output shape to inference.

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 every parameter is already documented, including the 40/35/25 weights and web defaults. The description restates the weights and mentions the option pool and FAST grants but adds no syntax, format, or interaction detail beyond the schema, so the baseline 3 applies.

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 specific verb and resource ("Splits founder equity") and names the exact inputs that drive it (weighted contribution scores, option pool, FAST grants, ARR multiple). An agent can distinguish this from calc_safe_dilution or calc_83b_qsbs_delaware by the contribution-score and FAST-grant mechanics, though no sibling is named explicitly.

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?

Usage is implied by the specificity of the calculation, and the closing caveats ("rule of thumb, not a market valuation", "illustrative, not legal advice") scope when the output is appropriate. However, no alternative tool is named and no when-not condition routes the agent elsewhere among the many calc_* siblings.

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