Calculate Vat Period

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context: it does not lock the period, it computes results from transactions, and it explicitly states 'does not change anything'. This goes beyond the annotations without contradicting them.

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?

Three tightly written sentences: hook/purpose first, factual context second, usage triggers third. No filler or repetition of schema fields. Every sentence earns its place.

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 simple read-only tool with one well-documented parameter and strong annotations, the description provides sufficient context: what it computes, why it exists, and when to use it. It does not detail the output structure, but the '9-box' phrasing already conveys the result shape, and there is no output schema requiring alignment.

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 single parameter period_id is already well documented, including a cross-reference to get_vat_periods. The description does not add additional parameter-specific meaning, so the baseline of 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?

The description states a specific verb 'Preview' and resource '9-box VAT breakdown' and immediately distinguishes the tool from lock_vat_period by clarifying it does NOT lock the period. It also explains the computation source ('period's transactions', 'same logic as the VAT page'), making the tool's role unambiguous.

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?

Provides explicit trigger examples ('what's my VAT for this quarter', 'show me the 9 boxes') and an explicit pre-workflow ('before lock_vat_period so they can check first'). This clearly tells an agent when to invoke this tool instead of others like get_vat_summary or lock_vat_period.

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