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

With no annotations, the description carries the burden. It clearly discloses that values are ignored, which is the key behavioral trait. It does not mention return format, edge cases, or side effects, but for a pure counting operation this is a reasonable disclosure.

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?

Two short sentences with no filler; the core action is front-loaded. It is concise, though slightly under-specified.

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 and no output schema or annotations, yet the description does not clarify how the parameters relate to the 'JSON object' being counted. It is ambiguous whether the tool counts keys in the input object or in the value of the 'json' parameter. This is a significant gap for correct invocation.

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 baseline is 3. The description adds the cross-cutting semantic that all parameter values are discarded, which is not evident from the individual schema descriptions. This helps an agent realize it can pass dummy values.

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 ('count') and resource ('keys in a JSON object') and adds a behavioral qualifier ('values discarded'). It is not a tautology and is distinguishable from siblings like validate-json, though it does not explicitly identify the input object as the set of provided parameters.

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 phrase 'values discarded' implies that callers need not supply meaningful values, which is a useful hint. However, it gives no explicit guidance on when to prefer this tool over alternatives or what conditions trigger its use.

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