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

No annotations are provided, so the description carries the full burden of behavioral disclosure. The description 'Format decimal' reveals nothing about how the tool behaves — no input handling, no output format, no edge cases or side effects. This is the lowest tier of behavioral opacity.

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 three words that mirror the name — this is under-specification, not conciseness. Every word is redundant with the tool name, so no sentence earns its place by adding information. A concise definition would still state the operation, input, and output in at least one substantive sentence.

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?

The tool has an empty input schema, no output schema, no annotations, and a tautological description. An agent has no way to know what value gets formatted, what formatting rules apply, or what the return value looks like. For a formatting tool in a catalog of thousands of siblings, this is completely inadequate.

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 input schema is an empty object with 0 parameters, so per baseline there is nothing for the description to document. However, a 'format decimal' tool with zero parameters is itself suspicious — the description should have disclosed how the target value is supplied (e.g., from context). The missing input mechanism is a completeness gap, but semantically there is no parameter meaning to add.

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 'Format Decimal: Format decimal.' is a pure tautology — every word merely restates the tool name. It does not specify what formatting is applied (rounding, thousands separators, fixed precision, scientific notation) or what input it operates on. Among dozens of sibling format-* tools (format-fixed, format-significant, format-thousands, format-scientific), there is nothing distinguishing this one.

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. With sibling tools like x402-format-fixed, x402-format-integer, and x402-format-significant, an agent cannot determine which tool fits a given formatting task. There is no context, no exclusions, and no mention of alternatives — only a vacuous restatement of the name.

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