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

With no annotations, the description carries the full burden of behavioral disclosure. It mentions 'Values discarded,' which is a trait, but it does not clarify the tool's safety profile (read-only vs side effects), the effect on other parameters, or whether it modifies any state. It also doesn't explain that the 'json' parameter is the primary input, which is a critical behavioral detail.

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?

The description is very concise (one sentence) and front-loaded with the primary action. However, it is under-specified for a tool with nine parameters; it lacks any structure or guidance about which parameter is the input. It is not appropriately sized because it omits critical information, making it more under-specified than concise.

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?

Given the complexity (9 parameters, no annotations, no output schema), the description is grossly inadequate. It does not explain which parameter to use, the expected input format, the return value, or any constraints. An agent cannot confidently invoke this tool correctly based on the description alone.

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, but the description adds no clarity about how parameters relate to the tool's purpose. The schema descriptions themselves are misleading (e.g., 'json' is described as 'to validate' rather than for counting keys). The description does not point to the 'json' parameter or explain the role of the other eight parameters, so it fails to compensate for the schema's ambiguity.

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 distinct from sibling tools like validate-json. However, it does not map to the actual parameters (9 unrelated string fields), leaving ambiguity about which parameter holds the JSON. It also fails to differentiate from siblings by name, though no sibling counts keys, so it is distinct.

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 conditions, exclusions, or related tools. The description only states what it does, not when it should be chosen, which is a significant gap given the large sibling list.

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