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

There are no annotations and no output schema, so the description carries the full behavioral burden. It does not disclose rounding behavior, return type, default decimal places, or why the claimed number input is absent from the input schema.

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 extremely short and the main action is front-loaded. The leading 'Format Fixed:' label repeats the tool name, but the rest of the sentence has no wasted content.

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 tool with no annotations and no output schema, this is not complete enough to invoke confidently: the description implies a number must be supplied while the schema accepts no parameters, and no sibling or output context resolves the ambiguity.

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 schema has zero properties, so the zero-parameter baseline applies and there is little parameter documentation to provide. The description adds only the conceptual meaning that this concerns formatting a number with fixed decimals, not a usable argument contract.

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 identifies a specific action ('format') and a clear target ('a number') with a defined mode ('fixed decimals'), so an agent understands the core purpose. It does not, however, differentiate this tool from closely related siblings like x402-to-fixed, x402-format-decimal, or x402-format-significant.

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 guidance or exclusions are provided. The agent is given no criteria for choosing this tool over the many sibling number-formatting tools and must infer the context from the name alone.

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