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

With no annotations, the description carries the behavioral burden, and it does disclose one useful trait: depth defaults to fully flat. It does not state whether the original array is mutated, what the return value looks like, or how invalid depths are handled.

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 are appropriately brief, but 'Flatten:' is redundant with the tool name and the instruction is vague. The default-depth detail is useful and front-loaded.

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 zero-parameter schema with no output schema or annotations, the description must explain how input is supplied; it only gestures at 'values' and 'depth' without specifying format. It is enough for coarse selection but not for reliable invocation.

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 lists zero parameters, yet the description tells the agent to 'Provide values and optional depth'. Without parameter names, types, or a way to pass the array, an agent cannot reliably construct the call; the description does not compensate for the schema gap.

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 identifies a clear operation and resource: flatten a nested array to a given depth. However, it repeats the tool name and does not explicitly differentiate itself from similar tools like x402-matrix-flatten or x402-json-flatten.

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?

It gives a partial usage instruction ('Provide values and optional depth'), but does not say when to prefer this tool over array, matrix, or JSON flattening alternatives, nor when not to use it.

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