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

With no annotations supplied, the description carries the burden of behavioral disclosure. It does explicitly say values are discarded, which is a meaningful behavioral trait, but it does not mention return format, side-effect safety, or behavior for an empty object or unknown keys.

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 with no filler; the primary action is front-loaded and the second sentence adds useful behavioral information. Every word earns its place.

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 annotations, and no output schema, the description is too thin. It does not explain how to supply the JSON object, what the return value looks like, or why the other parameters are present and discarded, leaving an agent to guess about 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?

Schema description coverage is 100%, so the baseline is 3. The description adds the general rule that values are discarded, which applies across all parameters, but it does not connect a specific parameter to the JSON object being counted; the json parameter's description says 'validate', which conflicts with the counting purpose.

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 clear operation ('Count keys') and target ('a JSON object'), and the note 'Values discarded' clarifies that values are irrelevant. It is reasonably distinguishable from siblings like validate-json, though it does not explicitly name them or resolve whether the object is passed as top-level arguments or via the json field.

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 when-to-use or when-not-to-use guidance, no mention of alternatives such as validate-json or hn-front-count, and no preconditions stated. The description leaves the agent to infer when this tool should be selected over sibling count/validation tools.

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