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

With no annotations provided, the description carries the behavioral burden. 'Values discarded' is a useful disclosure, and counting is an inherently read-only-sounding operation. However, it does not disclose return format, whether keys are counted recursively or top-level, behavior on invalid JSON, or any memory-related side effects hinted at by the tool name.

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, redundancy, or unnecessary details. The core verb and resource are front-loaded, and every word contributes to the meaning.

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 no output schema and no annotations, so the description must explain the return value and input contract. It only says 'Count keys in a JSON object' and never states what the output looks like, which input parameter to use, or how the memory-related name maps to the JSON-object behavior. That is too thin for a nine-parameter tool.

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 even though the description adds little parameter-specific detail. The description's 'values discarded' does clarify how parameter values are treated, but it does not identify which parameter is the JSON object or explain how the other eight parameters relate to the count.

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.' This is clear and distinguishes it from validation tools like validate-json. However, it does not say which of the nine schema parameters is the JSON object to count, and it does not explicitly differentiate from sibling count-like tools.

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 use this tool versus alternatives, no stated prerequisites, and no exclusions. The description only states what the tool does, not when it should be selected.

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