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 only states 'Values discarded,' which hints at a lack of persistence but gives no information about side effects, permissions, or what happens to non-JSON inputs. The schema hints that many parameters are 'discarded after the check,' but the description itself is almost completely silent on behavior.

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?

At one sentence, the description is extremely short, but it is under-specified rather than appropriately concise. It omits critical context about parameter usage and return values, and it lacks any structure that front-loads important constraints. Conciseness only works when the remaining text is sufficient, which it is not here.

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 9 parameters, no output schema, and no annotations. Despite this complexity, the description provides no information about expected inputs, how to invoke the tool correctly, or what the return value looks like. It is severely incomplete for an agent to use this tool safely and effectively.

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 parameter descriptions already mention discarding and shape checks, but the tool description adds no insight into how parameters relate to the counting function. It neither clarifies which parameter is the primary JSON input nor explains the varied parameter purposes, so it does not add value beyond the schema.

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'), but it does not clarify how this relates to the tool's 9 input parameters, several of which reference URLs, timezones, and other non-JSON data. The purpose is clear for a narrow JSON case but ambiguous for the rest of the schema. It does not distinguish from sibling tools like validate-json, but the counting intent 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?

No guidance is provided on when to use this tool vs alternatives. There is no mention of any preconditions, which parameter to provide, or whether a single parameter is expected at a time. The description offers no context to help an agent choose this tool over siblings.

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