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

Annotations already indicate readOnlyHint=true, so the agent knows no writes occur. The description adds transparency by calling it a 'STATELESS quote that persists nothing,' aligning perfectly with the annotation. It also notes that the result is a quote for later recording, which clarifies the non-persistent nature. No contradictions.

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 concise (3-4 sentences) and well-structured. It front-loads the core purpose and stateless nature, then provides key usage details and a sibling reference. Every sentence adds value, with no redundancy or fluff.

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 the tool's complexity (nested objects, no output schema), the description is complete. It explains what the tool returns (per-jurisdiction rates, total_tax_amount, totals), how to use the result (record with a sibling), and important input requirements. The detail about line item constraints compensates for the lack of output schema adequately.

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 coverage is 100%, providing baseline parameter descriptions. The description adds value by stating that each line item needs either a reference_product_id or product_category, a constraint not fully captured in the schema. It also reinforces that amounts are in the smallest currency unit (cents), which is already in the schema but pragmatically emphasized.

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 clearly states the tool's purpose: calculating sales tax/VAT for an order, emphasizing it is a stateless quote that persists nothing. It distinguishes itself from the numeral_create_transaction sibling by specifying that the calculation result should be recorded later. The verb 'calculate' and resource 'tax' are specific and 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?

The description explicitly instructs to record the calculation later with numeral_create_transaction using the returned calculation ID, providing a clear alternative for persistence. It also outlines required inputs (customer address and line items) and important details like currency units. However, it does not explicitly state when not to use this tool or provide complete scenarios for alternatives.

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