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

Annotations already establish readOnly/idempotent/non-destructive, and the description goes further by disclosing the actual computation rules (weekly hours over one full-time schedule; IRS 30-hour rule with a 120-hour monthly cap) and the modeling assumption that 'every month looks like the one entered'. That assumption is exactly the kind of caveat an agent needs; only rounding/precision and validation failure behavior are left unstated.

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, front-loaded with the verb and resource, then usage, then method, then return/assumption. No filler and no repetition of schema content.

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?

An output schema exists, so return formatting need not be explained; the description still notes that both counts are returned. Combined with the disclosed formulas and the month-uniformity assumption, an agent has everything needed to invoke this correctly.

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 coverage is 100%, so the baseline is 3, but the description earns credit above that by explaining the role of full_time_hours_per_week as the FTE divisor and how part-time groups feed the ACA 120-hour cap. It adds conceptual meaning rather than merely restating field names.

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 verb and resource ('Count full-time equivalent employees') plus a second concrete output (ACA count) and the regulatory threshold it decides. Nothing in the sibling list overlaps with this domain, so an agent can route here without ambiguity.

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?

Names three concrete use cases ('workforce planning, headcount reporting or checking applicable-large-employer status'), which gives clear when-to-use context. It stops short of stating exclusions or naming a sibling alternative for adjacent questions (e.g., hourly_to_salary or overtime_pay).

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