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

With no annotations, the description carries the full burden. It does disclose that values are discarded, which is a useful behavioral trait, but it omits critical details such as what the output looks like, error behavior, or side effects. The mismatch between the description and the schema (no clear JSON-object parameter) further undermines transparency.

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 (two sentences) and front-loaded with the purpose, but it is under-specified rather than appropriately concise. It omits essential information about input and output, making it more of a teaser than a functional specification.

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 9 parameters and no output schema, the description is completely inadequate. It does not explain how the parameters relate to the operation, what counts as a 'JSON object', or what the return value is. The complexity of the schema demands a much richer description to be usable.

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 coverage is 100%, so baseline is 3, but the description adds no value about parameters. It does not clarify which parameter is the JSON object; the 'json' parameter's schema description says 'JSON text to validate', which is inconsistent with the tool's counting purpose. The description fails to connect its purpose to any specific parameter, leaving the agent confused.

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 verb ('Count') and resource ('keys in a JSON object'), which is a distinct purpose. However, it fails to specify which of the 9 input parameters carries the JSON object, and the schema's 'json' parameter is described as 'validate' rather than 'count', creating ambiguity about how the tool is actually invoked.

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?

No guidance is given on when to use this tool versus alternatives like 'validate-json' or 'domain-shape'. The description does not mention context, prerequisites, or exclusions, leaving the agent to guess when this is the appropriate choice.

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