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

No annotations exist, so the description carries the full burden, yet it discloses nothing about return format, handling of negative/over-100 percentages, numeric-string parsing, or error behavior. The only behavioral note is the '5 free trial calls per signed wallet' line, which covers billing rather than operation semantics.

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?

One front-loaded sentence states the computation immediately, followed by a short promotional line. No bloat, though the free-trial tagline is noise relative to the tool's function.

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-input arithmetic helper with no annotations and no output schema, the description communicates the core computation, which is the essential piece. It remains incomplete on input formats and output shape, leaving ambiguity that a simple calculator description could easily resolve.

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% and both params are untyped strings, but the description does clarify the key semantic relationship: the percentage is taken 'of that value' (not an absolute amount). It still fails to specify expected string format (e.g., '10' vs '0.1') or whether the percent is subtracted from the original value.

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 concrete operation (decreasing a value by a percentage of itself) with a specific verb and result, which is more precise than a bare name restatement. The name plus description distinguishes it from x402-increase-by-percent, though the description never explicitly names that sibling as the alternative.

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 on when to use this tool versus the many sibling percent tools (x402-increase-by-percent, x402-discount, x402-percent-of, x402-percentage-change). The only extra sentence is a pricing/credits note, not usage context.

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