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

With no annotations provided, the description must fully disclose behavioral traits. It mentions 'Values discarded,' which is a behavioral note, but it does not state whether the operation is read-only, side-effect free, or what the return format is. This is insufficient for a tool with zero annotation coverage.

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 sentences and front-loaded with the core purpose. It is appropriately concise but sacrifices necessary detail about input and output, which affects other dimensions.

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 required ones, and no output schema. The description does not explain how to pass a JSON object, nor does it describe the return value or any constraints. The mismatch between the stated purpose and the actual schema makes this definition incomplete for an agent to invoke 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 has 100% description coverage, so each parameter is documented. However, the tool description adds no meaning to these parameters, and they appear unrelated to the stated purpose of counting keys in a JSON object (e.g., ref, city, zone). The description fails to bridge the gap between the flat parameters and the tool's core function, so the baseline of 3 is retained.

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 verb (count) and resource (keys in a JSON object), which distinguishes it from siblings like validate-json. However, it does not explain how the JSON object is provided, given the flat schema of 9 string parameters, leaving ambiguity about the actual input format.

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. The description does not mention any context, prerequisites, or exclusions, leaving the agent without direction on appropriate usage.

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