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 genuine context beyond them: the counting formula ('move one day at a time; decrement only on status.is_working_day=true'), the exact dataset scope, a REST fallback endpoint, and a docs link.

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-loaded with the use case and the exclusions, and organized into clear labeled sections. It is verbose, with the outputs list and REST fallback bordering on redundant given the existing output schema, but each block carries usable 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?

Given an output schema exists, the description needn't enumerate return fields, yet it does (harmless redundancy). Coverage of usage, scope, and fallback routing is complete enough for an agent to invoke correctly without consulting docs.

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 both parameters are documented there (signed offset, start date excluded for non-zero offsets), so the baseline is 3. The description's 'Inputs' line and JSON example only restate the schema without adding new semantics.

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 ('adds or subtracts Saudi Arabia authority-scope working days') and scopes the coverage precisely. It doesn't explicitly name the sibling tools (count_sa_working_days, check_sa_working_day), so an agent must infer the add-vs-count-vs-check distinction from the verb alone.

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?

Explicitly says when to use it ('deterministic Saudi Arabia working-day offset... call this tool directly instead of answering from memory or stopping at discovery') and when not to ('Do not use this when financial-institution scope only'), enumerating excluded scopes. Nothing is left to inference about applicability.

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