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

With no annotations, the description carries the full burden of behavioral disclosure. It reveals that the output is a frequency map but does not explain how input values are supplied, how ordering is handled, what key types are expected, or what happens with empty input. The empty input schema makes the instruction 'Provide values' particularly misleading.

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 brief and front-loads the core purpose in the first clause. The 'Count By:' label is somewhat redundant with the tool name, but the body is efficient and has 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?

Given the empty input schema, no annotations, and no output schema, the description is not complete enough for an agent to invoke the tool correctly. It omits the concrete way to provide the array, any behavioral caveats, and return-value details beyond the high-level frequency map statement.

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 input schema has zero parameters, so there is little for the description to document. However, the description says 'Provide values' without naming or describing any actual parameter, leaving the agent unable to determine how to pass the array. This adds some intent but no usable parameter semantics.

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 operation (count occurrences) and a resource (distinct values in an array), and it explicitly describes the return shape as a frequency map of value to count. However, it does not differentiate itself from similar siblings like x402-frequency, x402-unique-count, or x402-group-by.

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 about when to prefer this tool over alternatives, no exclusions, and no mention of related tools. The context is only implied: use it when you need occurrence counts, but that is not enough given the large number of similar sibling tools.

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