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

Annotations already mark this as read-only, idempotent, non-destructive, and closed-world, and the description adds substantial behavioral detail: exactly which cliff outputs are produced and how results expand when household_income is supplied. It also discloses the comparison against expired 2021-2025 enhanced rules and the MAGI-reduction calculation.

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 description is front-loaded with the primary cliff output and efficiently covers optional behavior. It is a single dense sentence, so slightly heavy, but every clause adds useful output or comparison information.

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 explains the return values in enough detail for correct invocation and interpretation. It also covers the optional household_income branch and the policy comparison context, which are the key behavioral complexities for this calculator.

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 five parameters are already well documented in the schema. The description adds the conditional meaning of household_income triggering extra outputs, but otherwise relies on the schema for parameter semantics; 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 calculation and scope: the dollar effect of the 400% FPL subsidy cliff for 2026, including cliff income, credit at 400%, credit at $1 more, and loss. This is clearly distinguishable from generic premium tax credit or poverty-level siblings, even without naming them.

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?

The description makes clear when the tool is useful: analyzing the returned subsidy cliff and, optionally, comparing 2026 rules with expired enhanced rules. It does not explicitly name when to choose a sibling like calculate_premium_tax_credit instead, but the cliff-specific framing gives strong usage context.

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