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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real value by scoping the calculation to specific tax heads and stating the result is 'line by line' itemized, which partly compensates for the missing output schema. It does not disclose assumptions, exclusions, or what happens with unsupported status/pay combinations.

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?

One dense sentence, front-loaded with the jurisdiction and the core comparison, with the component list in a compact parenthetical. No filler, though the leading 'Ireland:' label and trailing 'line by line.' are slightly fragmentary.

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 6-parameter calculator with high schema coverage, the description supplies the essential frame: two-year comparison, tax heads included, itemized output. Remaining gaps (assumptions, treatment of the enum statuses, whether PRSI/USC rates are 2026 or 2027 vintage) are modest given the schema carries parameter detail.

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 83%, so the schema already documents most parameters (gross pay, partner pay, renter, home carer, self-employed). The description's only added semantic is confirming rent credit is modeled, which corresponds to the 'renter' flag. 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?

The description names a specific output (take-home pay comparison for 2026 vs 2027 after Budget 2027) and enumerates the tax components in scope (income tax bands/credits, USC, PRSI, rent credit). An agent can tell this is a net-pay calculator, not a benefits/eligibility checker. It doesn't differentiate itself from siblings like ireland_rent_tax_credit, so it stops short of a 5.

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 only implied: the mention of 'Budget 2027' and the year-over-year framing suggests when it applies, but there is no explicit when-to-use/when-not guidance or pointer to alternatives such as ireland_rent_tax_credit for the rent-credit portion alone. Adequate but leaves routing to inference.

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