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

The description adds context beyond annotations: it notes the fee inclusion nuance, error-handling behavior ('never raises a protocol error — returns {error}'), and idempotent/read-only guarantee (though idempotent/readOnly are already in annotations). The error behavior and fee subtlety are extra value. No contradiction.

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 a single well-structured paragraph that front-loads the primary purpose as an imperative, then gives usage guidance, an example, and error behavior. No fluff—every sentence adds information. Slightly long but justified by complexity.

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 (6 params, some interdependent fee logic), the description covers the core formula, provides a concrete input/output example, explains the error behavior, and explicitly states the read-only/idempotent nature (authoritative even if annotations also mention it). With an output schema presentished, the example covers return structure. This is fully sufficient for an agent to invoke 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% with detailed descriptions, so baseline is 3. The description adds value by explaining the fee calculation nuance (not simply cost/(1-margin)) and providing a concrete example input that clarifies how parameters combine. This pushes it above baseline.

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 an explicit purpose: 'Work backwards from the margin you want to the price you must charge. FREE.' It clearly names the tool's function and distinguishes it from sibling margin_check by saying 'Not for checking one price you already have — that is margin_check.' The verb-resource pairing is specific.

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?

Directly states when to use: 'setting a price list' and explicitly excludes when not to use: 'Not for checking one price you already have — that is margin_check.' This is the clearest form of usage guidance.

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