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

Annotations already declare readOnly, idempotent, closed-world, non-destructive behavior. The description adds meaningful context beyond that: the result includes every dated period with legal basis, source and confidence, telling the agent it gets historical, provenance-tagged data rather than a single snapshot.

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?

A single dense sentence, front-loaded with the resource and followed by the returned fields. The parenthetical levy list is long but earns its place by delimiting scope; nothing is wasted or repeated.

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 carries the return-value burden and does so by enumerating rates, base, floor, ceiling, dated periods, legal basis, source and confidence. Combined with the fully described two-parameter schema, an agent has enough to call it 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 description coverage is 100%, so both parameters are already fully documented. The description restates the date semantics (in force on a date, default today) without adding format or edge-case detail beyond the schema — baseline 3.

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 the specific resource (statutory payroll contributions: pension, health, housing, work injury, training) and the exact data returned (employee/employer rates, base, floor, ceiling, dated periods with legal basis). It is clearly distinct from get_vat or get_payroll_tax by scope, though it never explicitly names a sibling to contrast with.

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 through content: an agent can infer this is the lookup for social-security rates on a given date, but there is no explicit when-to-use guidance versus get_payroll_tax or calculate_withholding_tax, and no exclusions or prerequisites stated.

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