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

The description adds significant behavioral context beyond the readOnly/idempotent/destructive annotations: it discloses that rates are live and identical to checkout, include GST, require prior resolution of product/options/quantity, and that suburb improves accuracy. There is no contradiction with 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 four sentences, all dense with purpose, usage, prerequisites, and a customer-facing instruction. It is front-loaded with the core function and each subsequent sentence earns its place without redundancy.

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?

Despite having no output schema, the description covers the core return value (exact cost), prerequisites, parameter hints, and special behavioral notes. It integrates well with sibling tools (vivid_product / vivid_price) and covers edge cases like free pickup, making it complete for a 7-parameter tool.

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 71%, and the description adds extra semantics by connecting parameters to workflows ('Resolve the product + size/options + quantity first'), noting suburb improves accuracy, and linking options to vivid_price.options shape. This goes beyond the schema's individual field descriptions.

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 returns the exact delivery/freight cost for an Australian postcode, matching the live rates from the vividads.com.au checkout. It distinguishes from the sibling vivid_delivery_estimate by emphasizing 'EXACT' and 'live rates' and specifying the shipping-rules apps and GST inclusion.

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 when-to-use guidance is given: 'Use whenever the customer asks what shipping/delivery costs.' It also provides prerequisites and sequencing ('Resolve the product + size/options + quantity first'), clarifies accuracy improvement with suburb, and includes a clear exclusion ('Never estimate freight yourself') and a required note about free pickup.

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