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

No annotations are provided, so the description carries the full behavioral burden. 'Values discarded' hints that only keys matter, but it does not disclose whether the count is top-level only or recursive, how invalid JSON is handled, what output is returned, or whether any state is retained. This is minimal for a tool with no annotations.

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 with the action front-loaded and zero filler. Every word earns its place, and the key behavioral point ('Values discarded') is included without redundancy.

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 no-annotation, no-output-schema tool with nine parameters, two sentences are insufficient. It does not specify which parameter is the JSON input, whether the count includes nested keys, what the return value looks like, or how errors are surfaced. The agent is left with too much ambiguity to confidently invoke the 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?

Although schema coverage is 100%, the description does not identify which of the nine string parameters should contain the JSON object. The schema's 'json' parameter is described as 'JSON text to validate', while the tool description says to count keys, creating a conflicting semantic signal. The description adds no parameter-level clarity.

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 clearly states a specific action ('Count keys') on a specific resource ('a JSON object'), and adds that values are discarded. This distinguishes it from generic validation tools like validate-json, though it does not explicitly name alternatives or clarify which parameter is the JSON object.

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 instead of siblings. There are no alternatives mentioned, no exclusions, and no context to help an agent decide between memory-key-count and related JSON/shape tools. An agent would have to infer usage from the 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.