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

With no annotations, the description carries the burden for behavioral disclosure. It indicates that values are discarded, implying no persistence or side effects, but it does not explicitly state whether the tool is read-only, whether it accesses external resources, or what failure behavior to expect.

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 a single, concise sentence with no redundant wording. It is well-structured and front-loaded.

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 omits crucial context: how to pass the JSON object, what the return value looks like, whether only the listed parameters count as keys, and the impact of additionalProperties being false. With 9 optional parameters and no output schema, this incompleteness is significant.

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?

The parameter descriptions are misleading and largely irrelevant to counting keys. For example, `json` is described as 'JSON text to validate; discarded after the check', which suggests validation rather than key counting, and other parameters reference unrelated domains. This actively harms comprehension instead of adding meaning.

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 the action ('Count keys in a JSON object') and explicitly notes that values are discarded. It is understandable on its own, though it does not explicitly differentiate from sibling tools or explain how the JSON object is supplied.

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 versus alternatives such as validate-json or search-query-len. There is no mention of appropriate inputs, limitations, or exclusions.

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