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

The 'Values discarded' phrase discloses that the tool does not retain or return the object's values, which is useful given no annotations are present. Still, it does not describe the return format, error behavior, or side effects, so full transparency is lacking.

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 and front-loaded, with two sentences that each earn their place. However, for a tool with nine optional parameters, this brevity leaves important invocation details unsaid.

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 a complex, multi-parameter schema, no output schema, and no annotations, so the description alone must carry the burden. Seven words are insufficient to clarify which input to pass, how the count is returned, and how this relates to the sibling tools.

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 the baseline applies: each parameter is already documented. The description adds the concept of counting JSON keys but does not explicitly direct the agent to the 'json' parameter or clarify why nine unrelated parameters are present.

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—Counting keys in a JSON object—and notes that values are discarded, which distinguishes it from validation and shape-checking siblings. However, it does not explain how the nine optional schema parameters map to this operation, leaving some ambiguity.

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 like validate-json or the various shape check tools. There are no usage conditions, no exclusions, and no mention of which parameter supplies the JSON object.

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