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

With no annotations, the description carries the transparency burden. It does disclose that values are discarded, which is a meaningful behavioral detail. However, it does not say whether nested keys are counted, how malformed JSON is handled, or whether the operation is read-only beyond the implication of counting.

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 concise: two short sentences with the core verb front-loaded. Every word contributes, and there is no redundant or filler content.

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 nine optional parameters, no annotations, and no output schema, this description is not complete enough for reliable invocation. The agent cannot determine which parameter supplies the JSON object, and the mismatch between the tool description and the 'json' parameter description leaves a significant gap.

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%, which usually sets a baseline of 3, but the description adds no parameter mapping. The schema's only JSON-related parameter, 'json', is described as 'JSON text to validate', which conflicts with the counting purpose and leaves the agent unsure which of the nine optional fields is the actual 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 clearly identifies the operation: count keys in a JSON object. The phrase 'Values discarded' adds useful contrast with tools like validate-json, but it does not explicitly distinguish itself from sibling tools by name.

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?

There is no explicit when-to-use or when-not-to-use guidance. The description implies the tool is for counting keys, but it never mentions alternatives or conditions under which another tool like validate-json would be preferred.

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