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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real value beyond that: the exact computation formula ('move one day at a time; decrement only on status.is_working_day=true'), the authority-scope coverage boundary, and a REST fallback endpoint with an explicit warning not to guess other paths.

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 critical routing sentence is front-loaded, which is good, but the description is bloated: the 'Outputs:' enumeration duplicates the output schema field-by-field, and the docs/fallback/formula lines, while useful, push the length well past what a small offset calculator needs. Several labelled sections could be trimmed without losing decision-relevant 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?

For a two-parameter deterministic calculator with an output schema and full annotation coverage, this is nearly complete: it discloses coverage scope, computation formula, a REST fallback, and documentation. The only real gap is that it explains return fields the output schema already defines and never clarifies its relationship to the count_/check_ siblings.

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 documented in the schema. The description restates the input names and gives one full JSON example (including the working_days=0 boundary), which adds marginal value but does not go beyond the schema's own examples and the 'signed offset; start date excluded for non-zero offsets' note.

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 with scope: 'Adds or subtracts Italy authority-scope working days in exact coverage' plus a 'deterministic Italy working-day offset'. The Italy scoping distinguishes it from the many country siblings, but the description never explicitly distinguishes it from check_it_working_day or count_it_working_days, which share the same country scope and differ only in operation.

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?

'Use this when you need a deterministic Italy working-day offset' gives clear when-to-use context, and the 'Do not use this when...' clause signals a scope limitation. However, it never names the obvious alternatives (count_it_working_days, check_it_working_day) or states the condition that selects between them, so the routing between sibling operations is left to inference.

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