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

Annotations already establish the safety profile (readOnly, idempotent, openWorld=false, non-destructive), and the description reinforces it with 'Pure arithmetic: no network access, nothing stored'. Beyond that it adds genuinely new behavioral facts: 10,000 draws, the exact reported metrics, determinism ('the same inputs and seed always return the same answer'), and the unit convention (dollars, fractions like 0.3 = 30 percent). No contradiction with annotations.

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?

Front-loaded with what the tool returns, then inputs, then units, then determinism and side-effect guarantees — a sensible order. It is long, and the exhaustive input enumeration partly duplicates the schema's 24 parameter descriptions, which is the only thing keeping it from a 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?

For a 24-parameter tool with no output schema and zero required parameters (presets supply defaults), the description carries the necessary weight: it explains the returned metrics, the preset-plus-override model, determinism, units, and the absence of side effects. Nothing an agent needs to invoke 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 baseline is 3, but the description adds real value beyond the schema: it confirms every preset field is individually overridable, lists the overridable domain (cash, credit line, receivables, backlog, crews, overhead, owner draw, monthly bills, enquiries, close rate, seasonality, job types, materials, deposit/payment terms, bad debt, tax, setbacks), and fixes the unit convention globally. That global units statement is not repeated in the schema.

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 precise verb and resource plus method and scope: 'Simulate the next 52 weeks of a small services business 10,000 times (Monte Carlo)'. It immediately enumerates what the simulation reports (shortfall probability, worst week, percentile cash bands, drivers, profit), which no sibling tool does. An agent can distinguish this from list_presets and rank_levers without opening a 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?

Usage is implied rather than stated: 'Start from a trade preset (excavation, plumbing, hvac, landscaping, roofing, or general) and override any input' tells the agent how to configure a run, and the preset names hint at list_presets. However, no sibling tool is named, there are no when-not conditions, and no guidance on when a Monte Carlo cash simulation is the right call versus rank_levers.

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