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

With no annotations provided, the description carries the transparency burden. 'Values discarded' is a genuinely useful behavioral disclosure, but the description does not explain error behavior, whether the count includes only top-level keys, or what the response looks like.

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 purpose is front-loaded and the second sentence adds behavioral nuance, so the definition is concise without being bloated.

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 nine optional parameters, no required parameters, no output schema, and no annotations, the description is too sparse. An agent cannot reliably determine whether to pass one or many parameters, where the JSON object comes from, or what the tool returns.

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. The description adds no per-parameter meaning and does not clarify how the nine optional fields relate to 'the JSON object' that is being counted.

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 and object: 'Count keys in a JSON object' and adds the useful constraint 'Values discarded.' It does not explicitly distinguish itself from sibling tools like validate-json, and the nine-parameter schema leaves room for confusion about which input is the JSON object.

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, no exclusions, and no mention of how to choose among the nine optional parameters. The only usage signal is the implied 'use when you need a key count,' which is not explicit enough.

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