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

With no annotations, the description must carry the full burden of behavioral disclosure. It only states 'Values discarded,' which hints that values are not returned, but it does not explain what happens to the other parameters, whether the operation is read-only, or what the response looks like. For a tool with 9 parameters, this is severely insufficient.

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 a single sentence, which is concise but under-specified for a tool with 9 parameters. It lacks structure and does not clarify the primary input or usage pattern. It is not appropriately sized for the complexity of the tool.

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 is incomplete for the tool's complexity. It does not explain which parameter represents the JSON object, how the other parameters are used, or what the output format is. There is no output schema, and the description does not compensate for this gap. An agent would struggle to call 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?

The input schema provides descriptions for all 9 parameters (100% coverage), each with context like 'discarded after the shape check.' The tool description adds no additional meaning beyond the schema, so the baseline of 3 is appropriate. However, the parameter descriptions themselves suggest the tool does validation, which contradicts the stated purpose of 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 specific action ('Count keys in a JSON object') and a side effect ('Values discarded'), but it does not indicate which of the 9 parameters is the JSON object. The parameters include unrelated inputs like ref, url, city, and host, making it ambiguous how to invoke the tool. It also does not differentiate it from sibling tools like validate-json.

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 provided on when to use this tool versus alternatives. It does not mention any context, prerequisites, or exclusions. An agent cannot determine when this tool is preferable to 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.