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

The description mentions that values are discarded, but it does not disclose return format, error behavior, read-only nature, or side effects. With no annotations, the agent has little information about what to expect beyond the count semantics.

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 with no fluff. However, it omits essential details such as which parameter is used, so brevity comes at the cost of clarity.

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?

The description does not explain the output, the meaning of key counting with nested objects, or how to handle invalid input. Given the large input schema and lack of output schema, important context is missing.

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 description does not map any input parameter to the JSON object to count. The 'json' parameter is present and likely intended, but its schema description refers to validation and discarding after a check, which is inconsistent with counting keys.

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 basic purpose: count keys in a JSON object and discard values. However, it does not specify which input parameter contains the JSON object, and the input schema includes many unrelated parameters, so the purpose is not fully actionable.

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 about when to use this tool versus alternatives such as validate-json or calc-eval. The description only states the operation, not the applicable context.

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