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

No annotations are supplied, so the description carries the full behavioral burden, yet it discloses nothing about rounding mode, how a string 'value' is parsed, whether output is a string or number, or error behavior on invalid input. The only added information is the free-trial notice, which is commercial rather than behavioral.

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 a short, front-loaded pair of sentences: the core purpose first, then the trial note. Nothing is redundant, though the emoji trial notice is boilerplate that consumes attention without aiding invocation.

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?

Given zero annotations, zero schema coverage, no output schema, and unusual string-typed numeric parameters, the definition leaves too much unexplained for reliable invocation. It should at minimum document input formats, the digits parameter's constraints, and the return shape.

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% for both parameters, so the description must compensate. It implies 'value' is the number and 'digits' is the significant-figure count, but that is a weak inference; it never explains why both are typed as strings, whether decimals/scientific notation are accepted, or the valid range for digits.

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: 'Format a number with significant figures.' An agent can tell this is a number-formatting utility. However, it does not distinguish itself from closely related siblings such as x402-sig-figs, x402-significant-digits, x402-number-precision, or x402-format-fixed, so the agent cannot choose among them from this text alone.

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 versus the many overlapping siblings (sig-figs, significant-digits, format-fixed, round-to, number-precision). The only extra sentence is a pricing/trial note, which is not usage guidance. The agent must infer applicability from the name.

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