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

With no annotations provided, the description carries the full burden of behavioral disclosure and fails entirely. It reveals nothing about output format, whether nested keys are included, ordering, duplicate handling, error behavior on invalid JSON, or side effects. A five-word tautology provides zero transparency about what calling this tool actually does.

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 nominally tiny ('JSON Keys: JSON Keys'), but this is under-specification rather than conciseness — the two halves redundantly restate the same information. Every word is wasted, and there is no front-loaded verb or operational sentence. It fails to earn even a single word's worth of value.

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 tool with no output schema, no annotations, and a single vaguely-described parameter, the description is the only source of operational information — and it is completely absent. An agent cannot determine expected input format, return shape, or semantics of 'keys'. Even accounting for the tool's simplicity, nothing needed for correct invocation is conveyed.

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 100% — the single parameter 'value' is documented in the schema (though only generically as 'Value to process'). Per the rubric, high schema coverage warrants a baseline of 3 even though the tool description adds nothing about the parameter. The description does not compensate for the schema's vagueness about expecting a JSON string, but it is not penalized for omitting what structured data already covers.

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 'JSON Keys: JSON Keys' is a pure tautology that restates the tool name without adding a single verb, action, or resource detail. It does not state what operation is performed (extract keys? count them? list top-level keys?), leaving the agent unable to distinguish it from siblings like x402-json-values or x402-json-path.

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?

The description provides no guidance whatsoever on when to invoke this tool versus alternatives. With dozens of JSON-related siblings (x402-json-flatten, x402-json-validate, x402-json-values, x402-json-type), an agent has no basis for selecting this tool. It does not mislead, so it stops short of a 1, but it is completely devoid of usage context.

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