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

With no annotations provided, the description must carry the behavioral transparency burden. It does disclose that values are discarded, which is useful, but it does not explain behavior for invalid JSON, nested objects, empty objects, or the exact return value. This is a significant gap for a no-annotation 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 very short and front-loaded: 'Count keys in a JSON object' immediately conveys the core purpose, and 'Values discarded' adds a meaningful behavioral signal. There is no fluff, though it could be slightly expanded with key usage information without becoming verbose.

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 annotations, no output schema, and nine parameters, so the description needs to compensate. It does not explain which parameter holds the JSON object, whether the count includes nested keys, or what the output shape looks like. This is insufficient for reliable 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; each parameter already has its own description. However, the tool description does not identify which of the nine parameters contains the JSON object whose keys are to be counted, leaving some selection burden on the agent despite the schema.

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 action ('Count keys') and target resource ('in a JSON object'), and the note 'Values discarded' distinguishes it from a validation tool like validate-json. However, it does not clarify whether counting is top-level only or nested, leaving some ambiguity.

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?

No guidance is given on when to use this tool versus siblings such as validate-json or other shape-check tools. The description implies it is for counting keys, but it does not state conditions, exclusions, or alternatives.

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