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

With no annotations, the description must carry the behavioral disclosure burden. It reveals that values are discarded, but it does not state what the tool returns, how invalid JSON is handled, or which input provides the JSON object. This is minimal disclosure.

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 very short and front-loaded: two sentences with no filler. It is appropriately concise for a simple counting operation, though it leaves important contextual details to the schema.

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?

Given no output schema, no annotations, and seven-plus parameters, the description is incomplete. It fails to identify which parameter should be used, what the output shape is, and what happens on invalid input.

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 parameter names and descriptions already document the inputs. The tool description does not connect 'JSON object' to the 'json' parameter, but the schema largely compensates.

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 uses a specific verb ('Count') and resource ('keys in a JSON object'), so an agent can tell this counts keys rather than validating or fetching. It doesn't explicitly name a sibling to differentiate from, but the action itself is distinct enough.

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 guidance about when to use this tool versus siblings like validate-json or domain-shape. 'Values discarded' implies a use case where only key names matter, but that is not made explicit.

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