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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds minimal behavioral context, only noting that it 'returns a decimal.' It does not explain edge cases (e.g., zero income) or other behavioral traits, but given the annotations, a 3 is appropriate.

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, front-loaded sentence containing only the essential information: the definition, formula, and output type. No wasted words.

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 with full schema coverage and an output schema, the description provides all necessary information: the formula and return type. There is no missing context for the agent to invoke the tool 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?

The description explicitly states 'savings divided by income,' which clarifies the exact roles of the two parameters beyond the sparse schema descriptions. This adds meaningful semantic value, ensuring the agent knows how the inputs relate.

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 defines what the tool does: it computes the fraction of income saved, providing the formula (savings divided by income) and the return type (decimal). This is specific and complete, distinguishing it from other tools by its unique calculation.

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 provides no guidance on when to use this tool versus alternatives. It does not mention suitable contexts or exclusions, and the long sibling list suggests many similar financial calculations, making this a clear gap.

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