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

With no annotations, the description must carry the burden. It discloses one relevant behavior, 'Values discarded', which tells callers not to depend on parameter values. However, it does not state the return value, any side effects, or whether this is a pure in-memory read, so transparency is only partial.

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 main action is first, and the behavioral note 'Values discarded' earns its place in the second sentence.

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 incomplete for an agent facing 9 optional parameters and no output schema. It never states which parameters constitute the JSON object to count, how to supply it, or what the tool returns, so a caller could reasonably pass the wrong input such as the 'json' string parameter.

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 hint that values are discarded, but it does not specify that the count applies to which of the 9 optional parameters are provided, nor how the JSON object should be passed.

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?

Description names a specific action and resource: 'Count keys in a JSON object. Values discarded.' This is clear and distinguishable from sibling tools like validate-json and shape-check tools. It loses a point because it does not explicitly state that the JSON object is the set of supplied arguments, leaving some ambiguity about the input target.

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 intended use is implied by the verb 'count keys' – use it when a JSON object's key count is needed. There are no explicit when-to-use/when-not-to-use instructions or references to alternatives among the sibling tools.

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