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

No annotations are provided, so the description carries full behavioral burden. It only states 'Values discarded' but gives no information about error handling, output format, or behavior on invalid JSON. The schema descriptions add confusion by saying values are 'discarded after the check' without connecting to counting keys.

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 one short sentence, which is concise, but it is under-specified and not front-loaded with the most critical information (which parameter to use). It sacrifices clarity for brevity.

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 9 optional parameters, no output schema, and no annotations, the description is grossly inadequate. It does not explain the return value, error behavior, or which parameter is essential. An agent cannot reliably use this tool.

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?

While schema coverage is 100%, the description adds no linkage between parameters and the tool's purpose. The 'json' parameter description ('JSON text to validate; discarded after the check') suggests validation, not key counting, and many other parameters are irrelevant to counting keys. The description fails to clarify which parameter is the input.

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 operation (count keys) and resource (JSON object), but it does not clarify which input parameter carries the JSON object. The schema lists 9 unrelated string parameters, so an agent cannot confidently determine how to invoke the tool.

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 provided on when to use this tool versus siblings like validate-json or domain-shape. The description does not mention any conditions, prerequisites, or alternatives.

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