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

No annotations are provided, so the description carries the full burden. It usefully discloses that values are discarded, but it does not state the return format, whether nested keys are counted, how invalid JSON is handled, or what happens when no keys are present. These are meaningful behavioral gaps.

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. The action is front-loaded ('Count keys in a JSON object'), and 'Values discarded' earns its place by conveying the central behavioral constraint without redundant explanation.

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?

Despite its simplicity, the description is incomplete for an agent. There is no output schema and no annotations, and the description does not state what a call returns, whether nested keys are counted, or how the 'JSON object' maps to the flat schema of nine optional string parameters. The parameter descriptions hint at the discard semantics, but the tool's contract remains ambiguous.

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 description coverage is 100%, giving a baseline of 3. The description adds value beyond the schema by explaining that all parameter values are irrelevant and only key presence matters, which clarifies why every schema description mentions 'discarded' and why all parameters are optional.

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 specific operation ('Count keys') on a specific resource ('a JSON object') and adds the meaningful behavioral detail that values are discarded. It is reasonably distinct from validation or URL-shape siblings, though it does not explicitly name or differentiate sibling tools.

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 use case is implied: use this tool when you need the number of keys in a JSON object rather than the values. However, there is no explicit guidance about when not to use it, what alternatives exist, or any preconditions, so the agent must infer usage from the terse description.

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