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

The description only mentions that 'values discarded', implying the tool ignores values in the JSON. It does not disclose side effects, error behavior, or whether it performs validation or other actions. With no annotations, this leaves significant behavioral ambiguity.

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 extremely concise (two sentences) and front-loaded, but it sacrifices necessary detail. It is not verbose, yet the brevity contributes to the ambiguity about parameters and behavior.

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 nine parameters, none required, and no output schema, the description is severely incomplete. It omits the output format, the expected JSON input location, and any edge-case handling, making it insufficient for an agent to use effectively.

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 description adds no explanation of how parameters relate to the counting operation. The schema provides per-parameter descriptions, but the tool description does not clarify which parameters are relevant or how they are used, failing to add meaning beyond the schema.

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 goal ('Count keys in a JSON object') but fails to specify which of the nine input parameters actually contains the JSON. The tool name hints at the purpose, but ambiguity about the input reduces clarity.

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 compared to alternatives. The description does not mention any conditions, use cases, or distinctions from sibling tools, leaving the agent to infer applicability.

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