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

With no annotations, the description carries the behavioral burden and does disclose one non-obvious trait: values are discarded rather than returned or retained. However, it does not state whether nested keys are counted, how invalid JSON is handled, or whether the operation is stateless.

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?

Two short sentences, with the primary action in the first sentence and a useful behavioral caveat in the second. There is no filler, and the information is front-loaded.

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 an agent to call this tool correctly and interpret the result, the description would need to explain which parameter carries the JSON, what the return value looks like, and how malformed JSON is treated. The schema lists several unrelated optional parameters, and nothing in the description reconciles them with the stated counting purpose.

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 each parameter, which supports the baseline 3. The description adds no parameter-level detail and does not clarify which of the many optional schema parameters should be supplied for the JSON object.

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 opens with a specific operation and resource: count keys in a JSON object. It does not explicitly differentiate from sibling tools like validate-json, but the counting behavior and 'Values discarded' note make the core purpose clear.

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 implies the tool is for obtaining a key count of a JSON object, but it gives no explicit when-to-use or when-not-to-use guidance. It also does not mention alternatives such as validate-json, leaving the agent to infer the right choice among many sibling shape/count tools.

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