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

Annotations already declare readOnly/idempotent/non-destructive and openWorld=false, so the safety profile is covered. The description adds what a calculator needs to add: it is a pure deterministic math operation and it spells out which quantities get computed plus the ownership formula. It stops short of stating assumptions like the pool being carved from founders' shares or behavior at the 30% pool cap, which the schema only partially covers.

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?

Two dense sentences: outputs first, then routing, then an optional interactive link. No restatement of the title, no filler, and the most decision-relevant information is front-loaded.

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 correctly compensates by naming the return values, and the sibling routing closes the main ambiguity for a family of overlapping finance calculators. Remaining gaps are minor: no statement of what happens at the pool maximum or of the pre-money/share-price inputs' assumptions, but the tool is simple enough that this is close to complete.

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, including the founders'-share note on option_pool_pct. The description mentions founder dilution and the investment/post-money formula, which adds light context but no syntax or edge-case guidance beyond the schema. Baseline 3 is appropriate.

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?

States a specific computation (pre-money to post-money for a single priced round) and enumerates exactly what it returns: post-money, price per share, new shares issued, investor ownership, founder dilution. That verb+resource+output framing makes it immediately distinguishable from sibling calculators.

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?

Explicitly scopes usage to a single priced round and routes the agent elsewhere for other cases: 'Use dilution for several rounds and option_pool for pool math.' Both alternatives and the condition selecting them are named, leaving no inference required.

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