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 only mentions 'Values discarded', which is a minor trait, but does not state what the tool returns, how it handles the various non-JSON parameters, or any side effects. This is insufficient for a tool with 9 parameters and no output schema.

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 a single, concise sentence that is front-loaded with the core purpose. It avoids verbosity, though the brevity contributes to the lack of context. It is not unnecessarily long, so the structure is acceptable.

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 tool has 9 parameters, no output schema, and no annotations, the description is far too brief to be complete. It does not explain the purpose of most parameters, the expected return value, or the conditions under which each parameter is used. An agent would struggle to invoke this tool correctly.

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 each parameter has a description in the schema. The tool description adds meaning only for the 'json' parameter by clarifying its purpose. It does not explain why other parameters like 'url' or 'city' are present, which is a gap beyond what the schema alone provides. Baseline 3 is appropriate.

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 ('Count keys') and resource ('in a JSON object'), and notes that values are discarded. However, the tool accepts 9 parameters, most of which (e.g., 'url', 'city', 'feed') have nothing to do with JSON objects, making the stated purpose ambiguous and incomplete. It also does not distinguish itself from sibling tools like 'validate-json' or 'search-query-len'.

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 versus alternatives. The description does not mention any conditions, exclusions, or relationships to sibling tools, leaving the agent to infer usage.

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