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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context: exact digit preservation with no binary float conversion, which tells the agent this is a precision-preserving formatter rather than a floating-point evaluator.

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?

Two tightly written sentences, front-loading the operation and then the behavioral guarantee. No filler or redundancy.

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?

With annotations covering safety and an output schema covering return values, the description only needs to convey purpose and the exactness guarantee, which it does. The one remaining gap is routing context relative to sibling math tools, but the core call guidance is complete.

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 description coverage is 100%, so the mode enum and the text length/digit-limit constraints are already documented in the schema. The description echoes the normalize/expand distinction but adds no syntax, format, or edge-case detail beyond what the structured fields provide.

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 (normalize/expand) and resource (decimal strings / exponent notation) and distinguishes the two directional operations clearly. It does not, however, differentiate itself from close siblings like scientific_evaluate or round_sig_figs, leaving the agent to infer which arithmetic tool applies.

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?

No when-to-use or when-not-to-use guidance is given beyond the schema's mode enum. Nothing tells the agent why to pick this over scientific_evaluate, round_decimal, or round_sig_figs, which all touch the same numeric territory.

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