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

With no annotations, the description carries the behavioral burden. 'Values discarded' is a useful disclosure that values are not retained in the result, but the description does not clearly state whether this is read-only, whether it has side effects on memory, or what the return value communicates beyond a 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 very concise, front-loaded, and free of filler. Most words add value, but slight confusion around 'JSON object' in relation to the supplied schema could have been removed with a short clarifying clause.

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, this description is under-specified. It does not say which input represents the JSON object, how to construct the object, or what the count value should be interpreted as, leaving the agent to infer major parts of the contract.

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 input schema already documents all nine parameters, giving a baseline of 3. The description adds the 'values discarded' semantic but does not explain how the declared flat parameters correspond to a JSON object or which parameter is the intended object to count.

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 adds a clear behavioral note that values are discarded. It is not explicitly differentiated from sibling tools such as validate-json, but the counting purpose is recognizable and distinct at a high level.

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?

There is no guidance about when to use this tool versus alternatives, no context for selection, and no exclusion of when it should not be used. Siblings like validate-json or shape tools are not referenced, so the agent receives no decision support.

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