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

With no annotations supplied, the description carries the behavioral burden. It does disclose that values are discarded, which is a useful trait, but it does not explain count semantics (top-level vs nested keys), invalid JSON behavior, or the return value, leaving meaningful ambiguity for an agent.

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 extremely concise: two short sentences with no filler. The core action is front-loaded, and 'Values discarded' earns its place by clarifying the tool's scope.

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?

For a tool with nine optional parameters, no annotations, and no output schema, a single-sentence description is insufficient. The agent is left to guess how to supply the JSON object, whether nested keys are counted, and what happens with invalid JSON, so the definition is not complete enough 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 coverage is 100%, so the baseline is 3. The description adds the concept of counting keys and discarding values, but it never connects this to the `json` parameter; several schema descriptions mention discarding inputs, which makes parameter selection less obvious rather than more clear.

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 clear action ('Count keys') on a specific resource ('a JSON object') and adds 'Values discarded' to signal that only structure matters, which helps distinguish it from validation/shape tools like validate-json. It is not fully unambiguous, though, because it never says which parameter supplies the JSON object or whether the count is top-level only.

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 when-to-use guidance or comparison to alternatives is provided. 'Values discarded' hints that the tool is useful when values are unimportant, but there is no explicit condition, prerequisite, or routing away from sibling tools with related purposes.

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