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

No annotations are present, so the description carries the full burden of behavioral disclosure. It only states the high-level transformation and does not explain output casing, prefix inclusion, accepted number ranges/types, or failure behavior.

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 one sentence with no filler, and the core operation appears immediately. It is appropriately short, though the opening phrase 'Format Hex Num' is redundant with the tool name.

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?

Despite low complexity, the description is not complete enough for invocation: there are no parameters defined, no output schema, no annotations, and no distinction from very similar tools like x402-to-hex. An agent cannot reliably know how to call it or what exact result to expect.

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 parameters, and the baseline for 0-param tools is 4. The description still adds the meaningful fact that the tool operates on 'a number,' which is more than the empty input schema provides, though it does not specify exactly how that number should be supplied.

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 uses a clear verb and resource: 'Format a number as hex.' It is understandable at a glance, but it does not differentiate this tool from closely related siblings like x402-to-hex or x402-format-binary, so it stops short of full clarity.

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?

There is no guidance about when to prefer this tool over alternatives such as x402-to-hex, x402-number-base, x402-format-binary, or x402-format-octal-num. The agent must infer selection criteria from the name alone, which is risky in this large sibling set.

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