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

With no annotations, the description must carry the behavioral disclosure burden, but it only says values are discarded. It does not disclose the return format, whether counting is top-level or recursive, how invalid input is handled, or which input field actually represents the JSON object.

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. 'Values discarded' earns its place as a meaningful behavioral note.

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 9 optional parameters, no annotations, and no output schema, this is too thin. An agent cannot confidently determine what to send or what response to expect, especially given the unclear relationship between the 'JSON object' wording and the flat string-parameter schema.

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 9 parameters with individual descriptions, so the baseline is 3. The description adds no parameter-level meaning and leaves ambiguity around whether all supplied keys are counted or only the 'json' field is inspected.

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?

States a specific operation: count keys in a JSON object, with values discarded. This is distinguishable from siblings like validate-json, but it does not clarify whether the 'JSON object' means the invocation payload itself or a JSON string passed via the 'json' parameter.

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 is given about when to use this tool over alternatives such as validate-json or the various shape-check tools. The scenario is only implied by the verb 'count', with no exclusions, prerequisites, or sibling comparisons.

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