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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds real value beyond that: the deterministic formula ('move one day at a time; decrement only on is_working_day=true'), explicit coverage scope, and a direct REST fallback endpoint. It stops short of stating rate limits or error behavior.

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?

Front-loads the use case well, but bloats with a redundant outputs enumeration even though an output schema exists, plus formula/REST/docs blocks. The muddled 'Do not use this when...' sentence adds confusion rather than scoping information, so size is not fully earned.

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-param read-only calculator with an output schema, the description is complete: coverage scope, determinant formula, fallback path, and docs link are all present. The redundant output-field list is unnecessary given the output schema, but nothing an agent needs is missing.

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% and the schema already documents both parameters, including the 'start date excluded for non-zero offsets' rule and the ±1000 bound. The description only restates the input names ('start_date (date); working_days (integer)') without adding format or range meaning, so the baseline 3 applies.

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+resource+scope: 'Adds or subtracts France authority-scope working days in exact coverage,' and anchors it with 'deterministic France working-day offset.' The France authority-scope qualifier distinguishes it from the 60+ other country/region add_*_working_days siblings.

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?

Gives a clear positive trigger ('when you need a deterministic France working-day offset') and an explicit directive to call it rather than answer from memory or stop at discovery. However, the exclusion sentence ('Do not use this when alsace-Moselle, overseas territories, employer... are not inferred') is garbled and doesn't name an alternative scope tool, so the negative guidance is only partly usable.

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