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

With no annotations, the description carries the full burden of behavioral disclosure. It does note that values are discarded, which is helpful, but it fails to clarify whether the count includes nested keys, how invalid JSON is handled, what the return format is, or whether the operation is purely read-only. This is a significant gap without 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?

Two terse sentences with no filler. The core operation is front-loaded, and the second sentence adds a useful behavioral note. Every word 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?

The description is too thin for a tool with nine heterogeneous parameters, no annotations, and no output schema. It does not specify which parameter holds the JSON object, how the count is returned, or how invalid inputs are handled, leaving an agent with insufficient information for correct 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?

Schema coverage is 100%, so the schema already documents all nine parameters individually. The description adds no parameter-specific information beyond referencing 'a JSON object', so the baseline of 3 is appropriate.

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 uses a specific verb ('Count') and a clear resource ('keys in a JSON object'), and explicitly states that values are discarded. This distinguishes it from siblings like validate-json and think-steps, which perform different operations.

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 explicit guidance is provided about when to use this tool versus its siblings, and no alternatives are mentioned. Usage is only implied by the tool's name and the operation described, which is enough to infer basic intent but not enough to make a confident selection among similar tools.

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