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

Without annotations, the description carries the burden of behavioral disclosure. It discloses that values are ignored ('Values discarded'), which is useful, but it does not describe the return format, behavior on invalid JSON, or whether the operation is read-only. These gaps matter because no output schema or annotations are present.

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 short sentences with no filler and the main action is front-loaded. Both sentences earn their place.

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 tool with no output schema and no annotations, the description omits the return value and error behavior, and it does not identify which of the nine optional parameters supplies the JSON object. The lack of parameter mapping is a significant gap.

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 coverage is 100%, so the schema already documents all parameters. The description adds no parameter-specific guidance beyond implying that a JSON object must be provided; the likely `json` parameter is described in the schema as 'JSON text to validate' rather than as a key-counting input, so the mapping is left to inference.

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 uses a specific verb and resource: 'Count keys in a JSON object.' It conveys the core operation and is not a tautology. However, it does not explicitly differentiate this from siblings such as validate-json, and it does not state whether nested keys are counted.

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?

The intended use is implied by the description: call when a JSON object's key count is needed. There is no explicit when-not-to-use guidance or reference to alternatives, even though siblings like validate-json overlap in the JSON-handling domain.

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