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

No annotations are present, so the description must carry the behavioral transparency burden. It discloses one behavior—'Values discarded'—but does not state side effects, return behavior, error handling, or whether the input JSON is modified. This is minimal transparency for a tool with no annotation support.

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 no filler: 'Count keys in a JSON object. Values discarded.' It front-loads the action and object and earns each word. Even though it is incomplete in other dimensions, it is appropriately concise.

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?

There is no output schema and no annotation context, but the description does not state what is returned, how keys are counted (top-level only vs. nested), which parameter to provide, or how malformed JSON is handled. With nine optional parameters, this is a significant completeness 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 description coverage is 100%, so the baseline is 3 even though the description itself adds little parameter meaning. However, the description never links 'JSON object' to a specific parameter, and the schema's `json` parameter says 'JSON text to validate' rather than 'JSON text to count keys from,' creating ambiguity. The high coverage prevents a lower score, but better linkage would have made this clearer.

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 action and resource: 'Count keys in a JSON object.' This is distinct from the sibling validate-json tool, which is about validity checking rather than counting. It is slightly weaker for not clarifying whether the JSON is supplied via the `json` parameter or is some internal/memory object, but the core purpose is clear.

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?

The description gives no explicit when-to-use guidance and does not mention alternatives such as validate-json for validation or search-query-len for counting query length. It also does not say which of the many optional parameters should be supplied, leaving the agent to guess how to invoke the tool. Any usage context is only weakly implied by the name and one-line description.

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