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

With no annotations, the description carries the full burden. It does disclose the key behavioral trait (truncation, never rounding) and the default decimal count of 2, plus a pricing note about 5 free calls per signed wallet. It omits return type, error behavior for non-numeric input, and what happens with negative numbers.

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?

Front-loaded definition with an example in one short sentence; the trial-call promo is secondary and placed last. Nothing is padded or redundant.

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 two-parameter utility with no output schema and no annotations, the core semantics and default are covered, but the description leaves gaps on output format and edge-case input handling that the schema does not fill.

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 0%, so compensation is expected. The description explains the meaning and default of 'decimals' but says nothing about 'value', and notably both parameters are typed as strings in the schema with no explanation of that or of accepted formats.

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 and resource ('Truncate Decimal: Cut a number down to decimals places') plus a worked example showing 3.14159 -> 3.14. The 'without rounding' clause implicitly separates it from rounding tools like x402-round-to, though no sibling is named explicitly.

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 example conveys the implied use case (displaying a value at fixed precision without rounding), but there is no explicit when-to-use guidance and no routing away from near-neighbours such as x402-round-to, x402-format-fixed, or x402-format-decimal.

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