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

With no annotations, the description carries the behavioral disclosure burden. It adds one useful behavioral trait: values are discarded, meaning the result is just a key count rather than a parsed object. However, it does not disclose the return shape, behavior on invalid or empty JSON, or whether the operation has any side effects beyond the discard note.

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 very compact and front-loaded: two short sentences with no filler. It is efficient, though the omission of input mapping and output details makes it slightly under-specified rather than optimally informative.

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 no annotations, no output schema, nine optional parameters, and a large set of sibling tools, this two-sentence description leaves important decisions unresolved: which parameter to provide, what the count is returned as, and what happens on invalid input. It is not complete enough for confident 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 description coverage is 100%, so the baseline is 3 even without parameter detail in the description. The description adds no explicit mapping between 'JSON object' and the 'json' string parameter, and its singular object language is somewhat at odds with a schema of nine optional string parameters.

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 gives a clear verb-resource pairing ('Count keys in a JSON object') and states that values are discarded, which conveys the core operation. However, it does not connect 'JSON object' to any of the nine input parameters, and the tool name suggests memory-related semantics that the description does not explain.

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?

There is no guidance about when to use this tool versus alternatives, and no sibling tools are mentioned. The description does not state conditions such as 'when you need only the number of keys' or 'instead of validate-json', leaving invocation decisions to inference.

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