Compute 13th-month pay under PD 851

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

The description adds significant behavioral context beyond the annotations: it states the computation is 'deterministic,' describes automatic pro-rating, and discloses that the tool returns coverage/exclusion notes plus the payment deadline. It also warns that the result should be verified, which sets accurate expectations about the tool's reliability. No contradiction with the readOnlyHint, idempotentHint, or destructiveHint annotations.

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 description is information-dense and front-loaded: the first sentence states the formula and scope, the second covers outputs and deadline, and the third adds necessary legal caveats. Every sentence contributes distinct value, and there is no filler or repetition of schema details.

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 single-parameter calculator with a full input schema and an output schema, the description is complete: it explains the formula, pro-rating, output contents, deadline, and the need to verify underlying legal texts. The presence of an output schema means return-value details do not need to be restated. The caveat about DOLE advisories also addresses the contextual risk of relying on the computation.

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?

The schema already provides 100% description coverage for the single parameter, including the definition of totalBasicSalary and the pro-rating behavior. The description reinforces the same meaning by stating the formula and the '÷ 12' operation, but it does not add meaning beyond what the schema already explains. A baseline of 3 is appropriate because the schema carries the parameter documentation burden.

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 a specific verb ('Computes') and resource ('13th-month-pay calculator under PD 851') and states the formula: total basic salary earned within the calendar year ÷ 12. It clearly differentiates itself from sibling compute tools like compute_deadline and compute_prescription by focusing on a specific statutory calculation.

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?

The description clearly indicates when to use the tool: for deterministic 13th-month-pay calculations under PD 851, including pro-rating for partial-year service. It also provides cautionary usage guidance by saying 'Verify the rule text and current DOLE advisories with the corpus before relying on it' and 'Not legal advice.' It does not explicitly name alternative tools or exclusion conditions, but the context is clear.

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