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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It adds one behavioral trait ('Values discarded') but does not state whether keys are counted recursively or top-level only, what the return value looks like, or how invalid JSON is handled.

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. The first sentence states the core operation and the second adds a relevant behavioral detail.

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?

With 9 optional parameters, no output schema, and no annotations, the description is too thin for an agent to invoke correctly. It omits which parameter carries the JSON object, whether key counting is recursive, and what result format to expect.

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 tool description adds no parameter meaning, and the schema descriptions themselves are partly inconsistent with the stated purpose: only 'json' relates to JSON, while ref, city, feed, and host appear unrelated. Still, the presence of full schema descriptions keeps this at the baseline.

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 phrase 'Values discarded' clarifies that value content is irrelevant, which distinguishes the operation from validation or retrieval tools. However, it never connects the operation to any schema parameter, so an agent still has to guess that 'json' is the relevant input.

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 on when to prefer this tool over siblings such as validate-json or search-query-len, and no exclusions or prerequisites are stated. The only implied usage is the operation itself, which is not enough for robust tool selection.

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