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

With no annotations, the description carries the behavioral burden, and it does disclose the key trait that values are discarded. However, it does not state whether the tool reads persistent memory, whether it has side effects, or what the return value looks like, which is a notable gap for a tool with no output schema.

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 front-loaded sentences with no filler, and both sentences contribute (the operation and the value-discarding behavior). It is concise, though the brevity comes at the cost of the missing context noted above.

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?

Given 9 optional parameters, no output schema, and no annotations, the description is under-specified. It does not explain the expected return, how the optional parameters combine to form the JSON object, or whether the count is based on the arguments versus an internal memory object, so an agent cannot confidently invoke it 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?

Schema coverage is 100%, so the baseline is 3, and the description adds no parameter-level meaning. The schema's per-parameter descriptions are comprehensive but describe values in unrelated tool contexts, leaving unclear how each optional string maps to the count; 'Values discarded' is the only relevant semantic hint.

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 and object ('Count keys in a JSON object') and adds the useful note that values are discarded, so it is not a tautology. However, it does not identify which JSON object is being counted (the call arguments, a memory store, or the `json` parameter) and does not differentiate itself from siblings 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 when-to-use or when-not-to-use guidance is provided, and no alternative tools are named. The only implied use case is 'need a key count,' which an agent would have to infer from the tool name and the generic first sentence.

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