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

There are no annotations, so the description carries the behavioral disclosure burden. “Values discarded” is a useful disclosure that inputs or values are not retained, but the description does not explain behavior on malformed JSON, whether the count is top-level only, what invalid input does, or how errors are surfaced.

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 short sentences, front-loaded with the verb and object, and both sentences earn their place. There is no filler or redundant restating of the tool name.

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?

Given 9 optional parameters, no annotations, no output schema, and no usage flow, the description is insufficiently complete. It does not tell the agent which parameter to pass the JSON in, what the return count means, or how to handle edge cases; agents must infer most behavior from the schema.

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 input schema already describes all 9 parameters, so this is a baseline 3. The description adds “JSON object” context, which hints at the `json` parameter, but it does not explicitly map the described JSON object to that parameter or clarify how the other parameters are ignored or involved.

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”, and adds the behavior “Values discarded.” It is clear enough to distinguish from validate-json or fetch-focused siblings, but it does not explicitly mention the top-level vs nested scope of counting, so it is not a perfect statement of purpose.

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 guidance about when to use this tool versus validate-json, domain-shape, or other sibling tools. There is no ‘when to use’, ‘when not to use’, or reference to an alternative tool.

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