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

With no annotations provided, the description carries the burden of behavioral disclosure and does reveal one useful behavior: values are discarded, so only keys matter. However, it does not state whether the operation is read-only, what happens on invalid JSON, or what the response contains.

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 two short sentences with no filler; the core action is front-loaded and the 'Values discarded' detail adds useful information. It is appropriately compact for the simple operation it names.

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 nine optional parameters, no required arguments, and no output schema, this description is too thin. It does not specify which parameter to pass, what the return value looks like, or how errors are handled, so an agent cannot confidently construct a valid 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?

Although schema description coverage is 100%, the parameter descriptions are not aligned with the stated purpose: the only JSON-related parameter is described as 'JSON text to validate', and the other eight optional strings seem unrelated. The description gives no hint about which parameter contains the JSON object whose keys are counted, leaving the schema confusing.

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 verb and resource ('Count keys in a JSON object') and adds a meaningful qualifier ('Values discarded'). It is clear what the tool computes, though it does not explicitly differentiate it from sibling tools like validate-json or domain-shape.

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 use this tool versus alternatives, nor any mention of exclusions or prerequisites. An agent must infer usage from the name and one-line description alone.

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