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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world, so the safety profile is covered. The description usefully adds that the computation is a month-by-month forward simulation producing two specific results, but it omits any horizon cap or assumption about how far the simulation runs.

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 core capability is front-loaded in the first sentence with zero preamble. The trailing promotional link to the full web calculator adds little for an agent and is the only wasted text.

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 carries the burden of explaining results and does so: months to gross-profit coverage plus bridging cash. For a deterministic four-parameter calculator with full schema coverage this is close to sufficient, missing only simulation-horizon or assumption caveats.

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%, with all four parameters (revenue, growthRatePct, fixedBurn, grossMarginPct) documented in the schema itself. The description references growth rate, gross margin and fixed burn narratively but adds no units, ranges, or interpretation beyond the schema, so the baseline of 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 gives a specific verb (simulate month by month) plus the resource and even the computed outputs: months until gross profit covers fixed burn and the cash needed to bridge the gap. That is far more concrete than a tautology, though it never names or distinguishes itself from near siblings like growth_runway_extension_simulator or rule_of_40_sandbox.

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 states the input conditions (given revenue growth rate and gross margin) but gives no when-to-use framing, no exclusions, and no pointer to any alternative runway/forecast sibling. An agent must infer the use case from the purpose alone.

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