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

With no annotations provided, the description carries the behavioral burden. It does disclose the key behavioral trait that values are ignored/discarded, and 'count keys' implies a read-only operation. However, it does not mention return format, error behavior, or whether any argument is required, leaving some transparency gaps.

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, front-loaded sentences with no repetition or fluff. It directly states the operation and the key behavioral constraint.

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 9 optional parameters, no output schema, and no annotations, yet the description never explains the relationship between the JSON object and those parameters, nor what exactly is returned. An agent cannot know whether the count refers to required arguments, all present keys, or some external object.

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. The description confirms that values are discarded, which aligns with the repeated 'discarded after...' notes in the schema. Yet it does not clarify how the 9 optional parameters map to the 'JSON object' being counted, so an agent could easily misidentify which value is the object.

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: count keys in a JSON object, and explicitly says values are discarded. This is clear enough to separate it from semantic tools like validate-json or normalize-url, though it does not explicitly name or contrast any sibling.

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 guidance about when to choose this tool over validate-json or any other sibling. It neither states a preferred context nor excludes alternatives, so an agent must infer usage entirely from the one-line purpose.

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