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 not say whether this is a pure computation or creates any state, what the response contains (per-person amount? total with tip?), how rounding is handled, or what happens when inputs are missing — all five parameters are optional.

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 functional sentence is short and front-loaded, which is good. The trailing free-trial-calls clause and emoji are promotional noise that consumes space without helping 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?

For a five-parameter, zero-coverage, no-output-schema tool, the description should at minimum define the ambiguous parameter pairs and state what is returned. It explains the concept but not enough for an agent to construct a correct call.

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% across five string parameters, so the description must compensate and does not. Worse, it leaves the overlap between 'tip' and 'tipPercent' and between 'bill' and 'amount' unresolved — an agent cannot tell which parameter to populate or whether they are alternatives.

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 (splits) and the exact inputs being split (bill plus tip percentage across a number of people). The intent is unambiguous. It does not distinguish itself from the sibling x402-tip, which an agent could reasonably confuse with this one.

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 when-to-use guidance, no prerequisites, and no reference to the nearby x402-tip sibling. The second clause is marketing (free trial calls per signed wallet), which tells an agent about billing, not about selecting or invoking the tool.

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