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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description discloses critical runtime behavior: it never raises a protocol error and instead returns an error object with instructions on how to fix invalid input. It also reinforces that every call is read-only and idempotent, making retry safe. This meaningfully supplements the structured metadata.

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 efficiently structured: a one-line purpose, a one-line break-even explanation, a concrete example, an explicit usage guideline, and an error/safety note. Every sentence earns its place and the most important information is front-loaded.

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 has four parameters, a full output schema, annotations, and related sibling tools, the description is complete: it covers purpose, use context, exclusions, error behavior, idempotency, and a sample input/output. No significant operational gap remains for an agent to select and invoke it correctly.

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%, so the parameter descriptions already carry the core burden. The description adds value with a fully worked example ('Typical input {"gross_margin_pct": 45, ...} returns ...') that demonstrates how the parameters combine and what output relationships look like, which is more than the schema alone provides.

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 opens with a specific verb and resource: 'Find the order value at which free shipping stops costing you money.' It clearly differentiates itself from sibling tools by explicitly naming rate_card as the alternative for non-free shipping cost, so the agent can distinguish this tool from its siblings.

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 says 'Use when setting or defending a free-shipping bar' and explicitly excludes the alternative case: 'Not for what shipping should cost when it is not free — that is rate_card.' This gives clear when-to-use and when-not-to-use guidance.

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