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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering safety. The description adds the key behavioral detail of halves always rounding up (away from zero), which is not in annotations. It also specifies per-mode count limits, providing useful context beyond 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 two sentences with no redundancy. The primary action is stated first, followed by mode details and the source link. Every sentence earns its place, and it is appropriately sized for the tool's simplicity.

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 rounding tool with a full input schema and an output schema indicated, the description covers the operation, modes, ranges, rounding rule, and even the source. Nothing essential for correct invocation is missing.

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 schema already documents all three parameters. The description reinforces the ranges and clarifies the rounding rule, which is not captured in the schema. This adds meaningful semantic value beyond the schema, especially for the half-rounding behavior.

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 states the tool rounds a number to decimal places or significant figures, and specifies the rounding rule (halves rounded away from zero). This distinguishes it from other calculator siblings and leaves no ambiguity about its function.

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 implies usage for rounding tasks and clearly defines the two modes (dp and sf) with their ranges. It does not explicitly mention alternatives or when not to use it, but the specificity makes the intended use obvious. No exclusions are stated, but the context is clear.

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