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

With no annotations, the description carries the full behavioral burden. It does disclose two useful traits beyond the schema: 0-based indexing and first-occurrence tie-breaking when the maximum repeats. It omits edge-case behavior (empty input, non-numeric content) and any statement about what the response looks like.

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 core definition is a single tight sentence placed first, with the tie-break rule immediately after. The trailing free-trial/payment note is promotional but carries real pricing context, so little is wasted.

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 small single-parameter tool with no output schema and no annotations, the description covers what it returns and the tie-break rule, but leaves the input encoding and empty/degenerate input behavior unexplained. An agent could not reliably construct a valid call from this alone.

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 schema coverage is 0% and the only parameter is typed as a bare string, so the encoding of the number list (comma-separated, JSON array, whitespace-delimited) is critical but completely undocumented. The description says only 'values' and 'largest number', weakly implying a collection of numeric items without resolving the format question.

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 and resource ('Return the 0-based position of the largest number in values'), which implicitly separates it from x402-find-max (returns the value) and x402-find-min-index. It never names those siblings, so the differentiation is inferred from the word 'position' rather than stated outright.

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 explicit when-to-use or when-not-to-use guidance, and no mention of the obvious alternatives (x402-find-max, x402-find-min-index). The use case is only implied by the returned value being an index, which is the minimum viable level.

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