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

With no annotations, the description carries the full behavioral burden; 'Values discarded' does add transparency about side-effect-free handling. However, it does not disclose the return shape, error behavior for malformed input, or whether nested keys are counted, so it is only minimally transparent.

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 with no filler; the core operation and the key behavioral point are front-loaded. It is slightly too terse to resolve the input ambiguity, so it loses a point.

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 nine optional parameters, no required fields, no output schema, and no annotations. The description does not explain which JSON object is being counted, what a successful call should include, or what the result looks like, leaving a high-complexity definition under-specified.

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 adds the important caveat that parameter values are irrelevant, but it does not clarify the role of the `json` parameter or any other field. Because of the ambiguity among nine optional parameters, this is a baseline-level contribution.

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 the second sentence clarifies that values are ignored. This is distinct from sibling validators like validate-json or fetch-status, but it does not explicitly identify which input parameter or object is the target, so it stops short of a 5.

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 when-to-use or when-not-to-use guidance is given, and no sibling alternatives are named. The tool's role among the many siblings, such as validate-json or search-query-len, is left entirely to inference.

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