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

With no annotations, the description must carry behavioral context, and 'Values discarded' does add the useful fact that values are ignored rather than returned. However, it does not clarify whether this is a read-only/unmodified operation, whether invalid JSON causes an error, or whether nested keys are included; the word 'discarded' is also ambiguous.

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, front-loaded with the core action and a clear qualifier. Every word earns its place; there is no filler or redundancy.

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 tool has nine optional parameters, no annotations, and no output schema, so the agent needs more than a two-sentence description. It is unclear which parameter to supply, what the return value looks like, how nesting is handled, and what happens with invalid JSON. These gaps make correct invocation materially uncertain.

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 and the schema fully documents the parameters. The description adds no parameter guidance and fails to identify the json parameter as the required input among the nine optional fields, though it does not repeat schema details.

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 names a specific operation and resource: count the keys of a JSON object, ignoring values. This clearly separates it from validation or URL-shape siblings at a coarse level. It falls short of a 5 because it never specifies which of the nine schema parameters carries the JSON object.

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 use case is implied: call this when only a key count is needed and values are irrelevant; alternatives such as validate-json are only distinguishable by semantic inference. No explicit when-to-use, when-not-to-use, or alternative tool is named.

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