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

No annotations are provided, so the description carries the full burden. It discloses only 'Values discarded', which hints at a read-only, non-persistent operation but says nothing about return format, error behavior, or side effects. For a tool with 9 parameters and no annotation support, this is a significant gap in behavioral disclosure.

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 that front-loads the core purpose ('Count keys in a JSON object'). It wastes no words, but the brevity comes at the cost of essential context. It is appropriately sized for a minimal statement, but the under-specification limits structural completeness.

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 the tool's complexity—9 optional parameters, no output schema, and no annotations—the description is woefully incomplete. It fails to explain what the tool actually does with the various inputs, whether it expects a JSON string, how the count is returned, or when to invoke it. An agent would have to infer most behavior from the schema, with no guidance on the overall operation.

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 all 9 parameters are individually described (e.g., 'json' is 'JSON text to validate; discarded after the check'). The description itself adds no parameter meaning—it does not explain how parameters relate to key counting. Since the schema already handles parameter documentation, the baseline of 3 is appropriate, but the description's silence about parameter roles prevents a higher score.

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 verb ('Count') and resource ('keys in a JSON object'), but it is ambiguous how this relates to the 9 input parameters, each of which is a separate string. It does not clarify which parameter(s) represent the JSON object to be counted, nor does it differentiate from overlapping siblings like validate-json or domain-shape. The line 'Values discarded' adds a detail, but the overall purpose is under-specified.

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 on when to use this tool versus any of the 27 siblings. It does not mention alternatives, exclusions, or contexts such as 'use when you need a key count from a JSON string'. The description provides no actionable usage direction.

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