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

With no annotations provided, the description carries the full burden. It does disclose one behavioral trait: values are discarded, so only key presence matters. However, it does not state whether the operation is read-only, what happens with invalid JSON, or what the output format is, though the main behavior is reasonably transparent for a simple counting tool.

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, both of which earn their place: the first states the operation, the second provides a key behavioral caveat. It is front-loaded and contains no filler.

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 having nine parameters, no output schema, and no annotations, the description is too thin to fully support reliable invocation. It fails to specify the return format, how the JSON object is supplied, and how errors are surfaced, making it incomplete for the tool's actual complexity.

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 baseline is 3. The description adds no parameter-level meaning beyond the schema and does not clarify which of the nine optional parameters represents the JSON object to count, leaving the mapping ambiguous.

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 clearly states a specific operation: count keys in a JSON object while discarding values. This is distinguishable from sibling tools like validate-json, but the description does not explicitly name or contrast any sibling.

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?

Usage is implied rather than stated: an agent can infer to call this when it needs the number of keys in a JSON object. There are no explicit when-to-use or when-not-to-use instructions, and no alternatives are mentioned despite relevant siblings like validate-json.

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