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

With no annotations, the description carries full behavioral burden. It does not disclose whether this is a pure calculation (no side effects), how outputs are formatted (e.g., percentage as a decimal vs. whole number), rounding behavior, or any edge cases. For a calculation tool, these details matter for correct interpretation of results.

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, concise sentence that front-loads the core purpose. It contains no fluff, but it could be slightly more structured to break down inputs and outputs.

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 calculation tool with no output schema and no annotations, the description is incomplete. It does not specify the return format, how to handle different currencies, or any caveats. An agent has to infer or test to get correct results, especially regarding output representation.

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 0%, so the description must compensate. It mentions 'original and final prices' which maps to two of the three parameters, but it does not describe the optional 'currency' parameter or any constraints. The description adds minimal value beyond the raw schema field names.

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 ('Calculate') and the exact outputs ('absolute savings' and 'effective discount percentage') from two inputs ('original and final prices'). This clearly distinguishes it from siblings which handle buy X pay Y, unit cost, dilution, pack comparisons, and normalization.

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?

Usage is implied by the description—use this when you have original and final prices and need savings/discount. However, no explicit alternatives or exclusions are provided, and it doesn't mention scenarios where siblings would be more appropriate, so it lacks the proactive routing seen in higher-scoring definitions.

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