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

Annotations already declare read-only, idempotent, non-destructive behavior, and the description adds substantive computation rules: honors +0.5, AP/IB +1.0 on passing grades, weighted/unweighted outputs, and credit defaults of 1 for high school and 3 for college. No behavior contradicts the 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?

Four sentences, front-loaded with the usage condition, followed by weighting rules, return/default behavior, and exclusions. Each sentence contributes directly to selecting and invoking the tool.

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 moderately complex calculator with an output schema and enum-rich inputs, the description supplies modes, weighting formulas, defaults, return behavior, and exclusions. Remaining details such as scale and limits are already in the schema, so the definition is complete enough for correct invocation.

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?

With 67% schema description coverage, the schema documents most enums and fields, while the description adds useful meaning for mode and level through weighting rules and default credits. The scale parameter's 4.0/4.3 distinction is left to the schema, so the description adds value but does not fully compensate for every parameter detail.

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?

States a specific verb and resource: compute GPA from letter grades and credits, covering high school weighted/unweighted and college unweighted. It explicitly excludes single test grades and school-specific formulas like UC or LSAC, which distinguishes it from sibling tools such as test_score_calculator.

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?

Provides explicit when-to-use guidance (student wants GPA from letter grades and credits) and when-not-to-use guidance (single test grade, school-specific formula such as UC or LSAC). Alternatives are described by task category rather than by exact sibling tool name, but the routing signal is clear.

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