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

With no annotations provided, the description must carry the full behavioral burden. It only discloses that values are discarded, but does not mention side effects, authentication requirements, rate limits, error handling, or what happens with invalid inputs. This is insufficient for a tool with many parameters.

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 concise at two short sentences with no filler, and the key fact ('Count keys in a JSON object') is front-loaded. However, it is under-specified, so conciseness is achieved at the cost of clarity.

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 required parameters, no output schema, and no annotations, the description is far too brief. It does not explain how the parameters relate to the stated purpose or what the output format is, leaving an agent unable to call the tool correctly in many cases.

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?

The input schema has 100% coverage, with each parameter described clearly (e.g., 'JSON text to validate; discarded after the check'). The tool description adds no additional meaning beyond the schema, so it meets the baseline for high schema coverage but does not enhance understanding.

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 'Count keys in a JSON object' which names a specific action and resource, but it is ambiguous given the input schema includes many unrelated parameters (url, city, feed, host, etc.) that are not about JSON objects. It does not differentiate from sibling tools like yaml-key-count or validate-json, leaving the agent uncertain about when this tool is appropriate.

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. The description does not mention any conditions, exclusions, or preferred contexts, which is a significant gap given the large set of sibling tools.

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