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

No annotations are provided, so the description carries the full burden. It does add genuinely useful non-schema context: the tool is paywalled with '5 free trial calls per signed wallet', which tells an agent to expect an auth/spend dimension. It says nothing about the return shape (string vs number) or error behavior for non-numeric input.

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?

Two short sentences, front-loaded with the operation and followed by the input guidance. The free-trial note is compact rather than wasteful. Minor noise from the emoji marker, but no filler.

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 tool with 0% schema coverage and no output schema, the description should state input types/ranges and what is returned. It covers the default but leaves the string-typed parameters and the output undefined, so an agent can still invoke it incorrectly.

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 the description must compensate. It does clarify that sigFigs is optional and defaults to 3, which the bare schema does not. However, it leaves both parameters typed as plain strings with no stated range, format, or whether sigFigs accepts values like '0' or negatives.

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 states a specific verb and resource: 'Round a number to a specified number of significant figures', and names the inputs. An agent knows exactly what computation happens. It does not distinguish itself from near-duplicate siblings such as x402-significant-digits, x402-format-significant, or x402-round-to.

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 pick this over the many rounding/formatting siblings. The only usage instruction is 'Provide value and optional sigFigs (default 3)', which describes invocation, not tool selection.

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