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

There are no annotations, so the description must carry behavioral disclosure. It does disclose that values are discarded, which hints at a side-effect-free counting operation, but it does not state return format, handling of invalid JSON, or whether all other parameters are ignored.

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, front-loaded sentences with no filler. The core action and the key behavioral qualifier both appear immediately.

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 nine parameters, no annotations, and no output schema, this description is too thin. It does not tell the agent which parameter to populate, what the return value looks like, or how invalid JSON is handled, so a correctly informed call is not guaranteed.

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 schema carries most of the parameter burden. The description adds 'count keys' and 'values discarded,' but leaves ambiguous which of the nine parameters is the JSON object to count and whether the others are simply ignored.

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 names a concrete operation ('Count keys') and a clear resource ('a JSON object'), and 'Values discarded' distinguishes it from validation/retrieval tools. It is not a 5 because the actual JSON input is not explicitly named and the schema includes many unrelated parameters.

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 on when to use this tool versus validate-json or other siblings; no exclusions or alternative routing. The only contextual hint is 'Values discarded,' which is not enough to choose among the listed tools.

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