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

With no annotations, the description carries the full burden of behavioral disclosure. It discloses that values are ignored/discarded, but it does not say whether nested keys are counted, how invalid or non-object input is handled, or what the return value looks like. This is a meaningful gap for a tool with no safety annotations.

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 core action is front-loaded. Every phrase earns its 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?

The tool has no output schema and many optional parameters, so the description needs to explain how input maps to the JSON object and what the result is. It only states the action, leaving critical invocation details unresolved.

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% parameter description coverage, so the baseline is 3, but the description does not identify which parameter should contain the JSON object. The 'json' parameter is described as 'JSON text to validate', not as the object to count, making it ambiguous how to invoke the tool.

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 and resource: 'Count keys in a JSON object.' It is not a tautology and is distinct in intent from siblings like validate-json, though it does not explicitly name any sibling or explain which input carries the object.

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?

'Values discarded' implies the tool is for cases where only key count matters and values can be ignored, but there is no explicit statement of when to use this tool versus validate-json or other shape-check siblings. Usage context is left mostly to inference.

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