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

No annotations are present, so the description carries full behavioral burden. It usefully discloses that values are discarded, but it does not state the return type, whether nested keys are counted, how invalid JSON is handled, or whether input is mutated. The schema's 'json' parameter description even says 'discarded after the check', which undercuts the counting behavior.

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 the action front-loaded, and 'Values discarded' adds meaningful behavioral context without filler. It is concise and readable, though the brevity omits essential invocation details.

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?

With no annotations, no output schema, and a confusing multi-parameter input schema, the description should identify which argument holds the JSON object and what the tool returns. It does neither, leaving an agent unable to reliably invoke the tool. The core operation and one behavioral hint are present, so it is not wholly inadequate, but significant gaps remain.

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 schema describes all parameters, but most (ref, url, city, feed, host, path) are unrelated to the tool's stated purpose and are described as discarded or used by other kinds of checks. The only plausible JSON-related parameter, json, is described as 'JSON text to validate; discarded after the check', not as the object whose keys are counted. The tool description does not clarify which parameter supplies the JSON object.

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 clearly states a specific action ('Count') and resource ('keys in a JSON object'), and 'Values discarded' indicates it is not a value-mutating or validating tool. It does not explicitly differentiate it from sibling tools like validate-json or hn-front-count, but the core purpose is recognizable.

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 such as validate-json or domain-shape. No prerequisites, exclusions, or sibling comparisons are provided, so an agent must infer usage solely from the short imperative.

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