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

With no annotations, the description carries the full burden of behavioral disclosure. It only mentions that values are discarded and does not explain how the JSON object is selected among the many parameters, what happens with non-JSON inputs, or any side effects. The behavior is largely opaque.

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 very short and front-loaded, which is good for conciseness, but it is under-specified. It lacks essential context about how to invoke the tool, making it incomplete rather than efficiently concise.

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 9 parameters, no required fields, and no output schema, the description is far too terse. It does not explain the relationship between the parameters and the counting operation, the expected output format, or edge cases. An agent would struggle to use this tool correctly.

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?

While schema coverage is 100%, the tool description does not map its 'JSON object' concept to any specific parameter (e.g., 'json'). The parameter descriptions are generic and inconsistent with the stated purpose (e.g., 'json' says 'validate' instead of 'count'), so the description adds little meaning and may confuse an agent about which parameter to supply.

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 ('Count') and resource ('keys in a JSON object'), which is clear and distinguishable from siblings like validate-json. However, it does not explicitly differentiate from tools that might also operate on JSON shapes, and the large set of unrelated parameters muddies the intent slightly.

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 on when to use this tool versus alternatives, nor does it mention any conditions, prerequisites, or exclusions. An agent would have no idea whether this is preferred over validate-json or other shape-checking tools.

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