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

With no annotations present, the description carries the behavioral burden. 'Values discarded' is a useful disclosure, and several parameter descriptions reinforce a discard-and-forget behavior. However, the description does not explain whether keys are counted recursively, whether malformed JSON produces an error or empty result, or whether any state is changed.

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, fully front-loaded with the primary verb and object. It contains no filler and every word contributes a distinct point: the operation and the value-handling behavior.

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 tool has nine optional parameters, no annotations, and no output schema, yet the description provides only one line of functional information. It fails to state the return format, whether the count is top-level or nested, which parameter supplies the JSON, or how invalid inputs are handled. This leaves significant gaps for an agent trying to invoke the 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?

Schema coverage is 100%, so the baseline is 3 even without extra parameter details in the description. The description adds the general concept of counting keys and discarding values, but it does not clarify which of the many string parameters is the JSON object to count. This ambiguity limits the description's added value.

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 action and resource: 'Count keys in a JSON object.' It also adds the meaningful distinction that values are discarded, which clarifies the tool is about key counting rather than parsing or validation. However, it does not explicitly distinguish itself from sibling tools like validate-json or hn-front-count.

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 usage when a JSON key count is needed and values are irrelevant, but it provides no explicit when-to-use or when-not-to-use guidance. No alternatives are named, so an agent must infer that this is not the tool for validation or fetching.

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