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

With no annotations, the description carries the burden. 'Values discarded' is a genuine behavioral disclosure (values won't be used for domain operations), and 'count' implies a read-only operation. However, it does not state the response format, error behavior, or whether any of the listed params are privileged.

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, no filler, and the main action is front-loaded. It is concise, but slightly under-specified for the size of the schema.

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?

For a 9-parameter tool with no required params and no output schema, the description is thin. It doesn't specify that the tool returns a count, demonstrate a call, or clarify that the input object is the tool-call arguments. The 100% schema coverage offsets this partly, so the description is minimally adequate but not complete.

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?

All 9 parameters are documented in the schema (100% coverage), so the baseline is 3. The description adds the key cross-cutting semantic that values are irrelevant; only key presence matters. It does not, however, explain how the individual params relate to the 'JSON object' being counted.

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 names a specific operation (count keys) and resource (a JSON object), and the phrase 'Values discarded' clarifies that values are ignored. It does not explicitly distinguish this from sibling validation/shape tools, and leaves open whether the counted object is the arguments payload or one of the string params, so it is clear but not fully differentiated.

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 choose this tool over siblings such as validate-json, domain-shape, or search-query-len. The description simply restates the function; any use-case inference is left entirely to the agent.

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