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

With no annotations, the description carries the full burden, and it does disclose that values are discarded. However, it does not describe the output format, side effects, or whether state is preserved or modified.

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 brief, front-loaded, and free of filler. It is slightly too terse for the tool's complexity, but as concise prose it is structured well.

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?

With no output schema and no annotations, an agent cannot infer the return value or know which parameter supplies the JSON object. The description is too minimal to fully support correct invocation for a tool with 9 optional parameters.

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?

The schema already documents all nine parameters clearly, so the baseline is 3. The description adds no connection between 'JSON object' and the `json` parameter, and it does not explain how the other optional parameters relate to the count.

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 resource ('a JSON object'), and 'Values discarded' adds useful scope. It is clear but does not differentiate itself from siblings such as validate-json beyond the word 'count.'

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 mention of when it should not be used. The 9 optional parameters also make it unclear how an agent is supposed to select the relevant input.

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