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

No annotations are present, so the description carries the burden. It does contribute one behavioral fact—values are discarded—but it does not state whether the operation is read-only, what happens on invalid JSON, or whether any memory state is changed. The disclosure is present but minimal.

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 action is front-loaded and the behavioral qualifier follows immediately. Every word earns its place.

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 multiple optional string parameters, no annotations, and no output schema, this one-line description is not enough for correct invocation. It never says which parameter contains the JSON object or what return value to expect (count integer? string?), leaving an agent to guess.

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 does not explicitly map 'JSON object' to the json parameter, and the json parameter's own description ('JSON text to validate; discarded after the check') is only an indirect match. The many unrelated string parameters create ambiguity, but the schema at least describes each one.

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 concrete operation—counting keys in a JSON object—and the qualifier 'Values discarded' adds scope. It is less clear about how the JSON object is supplied (which parameter), and the name suggests memory keys while the description says JSON object, so it does not fully disambiguate from siblings like validate-json.

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 when-to-use guidance, no exclusion, and no mention of alternative tools such as validate-json or search-query-len. The only implied context is 'when a key count is needed,' which is not enough to route an agent confidently.

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