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

With no annotations provided, the description carries the full burden. 'Values discarded' is a useful behavioral disclosure beyond the tool name, indicating values are intentionally ignored. However, it does not describe edge cases such as nested keys, invalid input handling, or whether the count is top-level only, so transparency is incomplete.

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 a single, front-loaded sentence with no wasted words. It states the core action and the most important behavioral qualifier ('Values discarded') efficiently.

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?

The definition is adequate for a simple count operation but leaves notable gaps: no output schema or return format description, no explicit statement about which input is 'the JSON object,' and no guidance on nested key counting. The absent annotations increase the need for more context, so a mid-range score is appropriate.

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 baseline is 3. The description adds a global 'Values discarded' rule that aligns with the schema's repeated 'discarded' notes, but it does not clarify which parameter represents the JSON object to count or how the many heterogeneous parameters relate to the counting operation. It is minimally sufficient but not genuinely helpful.

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 verb and resource: 'Count keys in a JSON object.' The additional 'Values discarded' clarifies that values are irrelevant, helping distinguish it from siblings like validate-json or domain-shape. This is a clear, specific purpose statement.

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?

The purpose implies when to use the tool: when an agent needs a count of keys in a JSON object. However, there is no explicit guidance about when not to use it, no mention of alternatives, and no routing among the many sibling tools. It is acceptable but relies on inference.

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