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

With no annotations, the description carries the behavioral disclosure burden. 'Values discarded' is a useful trait because it tells the agent the tool will not preserve or return values, and 'count' implies a read-only action. However, it does not mention error behavior, whether nested keys are counted, return format, or any side effects.

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 no filler. The core verb 'Count' is front-loaded, and 'Values discarded' is a compact additional constraint that earns its place.

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?

Despite the simplicity of the one-line description, the tool has 9 optional parameters, no output schema, and no annotations. The description does not state what the tool returns, which parameter should hold the JSON, how invalid JSON is handled, or whether the count includes nested keys, leaving too much unspecified for reliable invocation.

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?

The schema has 100% parameter description coverage, so the schema already documents each parameter. The tool description does not add meaningful parameter semantics beyond saying 'JSON object', which loosely aligns with the json parameter, but it does not clarify the role of the many other unrelated parameters.

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 operation: count keys in a JSON object, and explicitly says values are discarded. This distinguishes it from validation-focused siblings like validate-json, though it does not name any sibling or explain scope more precisely.

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 guidance is given about when to use this tool versus alternatives. It does not mention which sibling to prefer for validation, shape checking, or other JSON-related tasks, so the agent has to infer usage from the tool name and description alone.

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