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

With no annotations provided, the description carries the full burden. 'Values discarded' usefully signals that values are not retained, but it does not disclose whether it counts top-level keys or nested keys, whether any state is persisted, what happens on invalid JSON, or what the output format is.

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 extremely short, front-loaded with the verb and resource, and contains no filler. It is efficient, though arguably too terse to fully support a nine-parameter tool.

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 no output schema, so the description should explain what the caller will receive; it does not. It also fails to explain how to select among the many input parameters or how values are discarded, leaving an agent unable to reliably 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 description coverage is 100%, so each parameter has some description. However, the tool description does not clarify which of the nine parameters supplies the JSON object or how the unrelated-looking parameters such as ref, url, city, and route map to 'Count keys in a JSON object.' The schema carries most of the parameter burden, but the mapping remains unclear.

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 and resource: 'Count keys in a JSON object.' This is directly meaningful and distinct from a vague name alone. However, it does not differentiate from sibling tools like validate-json, domain-shape, or hn-front-count, so it is not fully positioned among alternatives.

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 such as validate-json or other shape-related tools. No conditions, exclusions, or contextual hints are provided beyond the basic action.

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