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

The description reveals that values are discarded, which is a behavioral trait, but it does not disclose output format, error handling, or which parameter is used. With no annotations, the description carries the full burden, and it is insufficient for a tool with 9 optional parameters.

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 sentences with no fluff, clearly front-loading the purpose. However, given the tool's complexity (9 parameters, no output schema), this brevity may border on under-specification rather than conciseness.

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 description is inadequate for a tool with 9 parameters, no output schema, and no annotations. It does not explain how to provide the JSON object, what the output looks like, or when to choose this tool. An agent would struggle to invoke it correctly.

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 schema already provides descriptions for all 9 parameters (100% coverage), so the description adds no additional parameter-level information. However, the tool description's mention of 'JSON object' does not clarify which parameter maps to that, so the baseline of 3 is appropriate.

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 clear action (count keys) and resource (JSON object), but it does not specify which of the 9 parameters contains the JSON object. The 'json' parameter description mentions validation rather than key counting, creating ambiguity. The core purpose is identifiable but the input mapping is unclear.

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 provided on when to use this tool versus alternatives like validate-json or domain-shape. The description does not mention any conditions, exclusions, or alternative tools, leaving the agent to guess.

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