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

With no annotations, the description carries the behavioral disclosure burden. 'Values discarded' is a useful transparency note indicating no retention, but it does not disclose the return format, error behavior, or side effects beyond the count.

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 no filler: the core action comes first and the boundary condition ('values discarded') immediately follows. Every word earns its place.

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 nine optional parameters and no output schema or annotations, the description is too thin. It does not explain what the tool returns, which parameter to pass, or how it behaves when the JSON is malformed or the object is empty, so an agent has insufficient context to invoke it reliably.

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 description coverage is 100%, so the schema already documents all nine optional parameters. The tool description adds the notion that a JSON object's keys are counted, but it does not explicitly map 'json' (or any other parameter) to that object, leaving some ambiguity in a schema with no required parameters.

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 operation ('count keys') and resource ('JSON object') and notes that values are discarded. It is clear and avoids tautology, but it does not name related siblings such as validate-json or explain how this differs from them.

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 for when to use this tool versus the many sibling tools. There is no mention of what kind of JSON input is acceptable, whether the json parameter is the intended input, or when another sibling would be more appropriate.

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