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

Goes well beyond the readOnly/idempotent annotations by disclosing the algorithm ('move one day at a time; decrement only on is_working_day=true'), the non-inferred schedule boundaries, a REST fallback URL, and documentation link. This is substantive behavioral context the annotations cannot convey.

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 trigger and exclusion, which is good, but the 'Outputs:' field list duplicates the existing output schema and the formula/REST/docs lines pad an otherwise tight definition. The core guidance is buried among redundant enumerations.

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 2-parameter calculator with an output schema and full annotations, the definition covers trigger, exclusions, computation, and fallback. Minor confusion in the 'cuti bersama' exclusion phrasing, and the output list is redundant, 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%, so both parameters are already documented, including the signed-offset/exclusion semantics. The description's 'Inputs:' line merely restates types, adding nothing beyond the schema, so 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 ('adds or subtracts') plus resource ('Indonesia authority-scope working days') and scope ('exact coverage'). An agent can distinguish this from the many sibling add_*_working_days tools purely by jurisdiction.

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?

Explicit 'Use this when...' trigger, a directive to call directly rather than answer from memory, and an explicit 'Do not use this when...' exclusion covering cuti bersama/ASN/employer-specific schedules. Both the positive and negative conditions are stated.

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