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

With no annotations, the description carries the full load; it discloses the transformation and the pricing model (5 free trial calls per signed wallet), which is genuinely useful behavioral context. However, it says nothing about return format, behavior on non-numeric input, decimal handling, or what happens once the free trial is exhausted.

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, with no filler. The free-trial note is compact though slightly promotional for a description field.

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 trivial one-parameter tool the bar is low, but with no annotations, no output schema, and no parameter documentation, the description should state the accepted input format and the returned shape. Those gaps leave an agent guessing whether to pass "1234567.89" or "1,234,567.89".

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 single parameter is 0% documented in the schema, so the description must compensate and largely does not: it says "a number" while the schema types value as a string, leaving whether decimals, negatives, existing separators, or currency symbols are accepted entirely unclear.

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 gives a concrete verb and resource ("Add thousands separators to a number"), so the agent knows the transformation performed. It does not differentiate from close siblings such as x402-format-thousands or x402-format-integer, which appear to do the same thing.

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 statement of when to use this tool versus the many numeric-formatting siblings, and no mention of the condition that this applies only to numeric input. The only usage-adjacent sentence is a pricing trial note, not selection guidance.

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