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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the safety profile is clear. The description adds real value by disclosing the calculation basis (official 2026 income limits, +€30 from January 2027, the 60% rule) and the fact that the result is a weekly tax-free estimate. It stops short of saying what happens when an income exceeds the limits (zero entitlement?) or whether the estimate handles couples and pensions correctly, which is the detail that matters most for a calculator.

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 front-loaded sentence: jurisdiction, action, benefit, output nature, inputs, and method, in that order. It is dense but every clause carries information; the only friction is that the parenthetical rule details make it a long single sentence.

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 does its job by characterizing the return as a weekly tax-free estimate, and it explains the governing rules that determine the value. The gaps are minor: no treatment of partner income, pension, or other weekly income as eligibility levers, and no statement of what a nil entitlement looks like.

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 schema already defines all eight parameters including units and the 2026/2027 enum. The description restates three of them (gross pay, number of children, hours) without adding unit, format, or interaction guidance beyond the schema. 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 verb and resource ('estimate the Working Family Payment') plus the jurisdiction and output cadence, so an agent can tell it apart from siblings like ireland_carers_allowance or ireland_fuel_allowance. It never explicitly says how it differs from ireland_what_can_i_claim, but the tool name and sentence make the target benefit unambiguous.

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 inputs imply the applicable situation (family, children, hours worked), but there is no explicit when-to-use/when-not statement and no named alternative for adjacent questions such as what-else-can-I-claim. An agent can infer the trigger conditions but must reason about them from the parameter list rather than the text.

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