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

With no annotations, the description carries the full burden. It discloses one trait—'Values discarded'—but says nothing about side effects, permissions, error handling, or whether the operation is read-only. For a tool with 9 parameters and no output schema, this is insufficient transparency.

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 (two short sentences) and front-loads the core action, but brevity comes at the expense of necessary clarity. Every sentence does not earn its place because the first sentence alone is insufficient to guide correct invocation.

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?

For a tool with 9 optional parameters, no output schema, and no annotations, the description is severely incomplete. It fails to specify which parameter to use, what the return value represents, or how to handle the object input. An agent cannot reliably call this tool correctly based on the description.

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% (all properties have descriptions), so the baseline is 3, but the parameter descriptions are generic and misaligned with the tool's purpose. For example, the 'json' parameter is described as 'JSON text to validate', which is misleading for a key-counting tool. The description does not clarify which parameter holds the JSON object, and the parameter meanings do 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 clear verb+resource ('Count keys in a JSON object') and notes that values are discarded, which is distinctive. However, the input schema contains 9 unrelated string parameters (e.g., ref, url, city) that do not clearly map to the 'JSON object' the tool is supposed to count. The purpose is clear conceptually but ambiguous operationally, which prevents a higher score.

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 given on when to use this tool versus alternatives like 'validate-json' or 'domain-shape'. There is no mention of context, prerequisites, or exclusion criteria, leaving the agent to infer when counting keys would be appropriate.

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