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

No annotations are provided, so the description must disclose behavior. It only says 'text discarded,' which is a vague statement about input handling and does not reveal return values, side effects, or error conditions. The tool's behavior is essentially undisclosed.

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 extremely short (one line) and under-specified. While it is concise in length, it omits essential information and does not earn its place; it is more a placeholder than a meaningful description.

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 parameters, no output schema, and no annotations, the description is grossly incomplete. It does not state what the tool returns, how to invoke it correctly, or which parameter is relevant, making it impossible for an agent to use it effectively.

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 schema descriptions for each parameter are detailed (e.g., 'Git ref name; discarded after the shape check'), but the tool description does not connect these to the counting purpose. With 100% schema coverage the baseline is 3, but the description fails to clarify which parameter holds the text to be counted, so it adds no value beyond the schema and actually obscures the relationship.

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 'UTF-16 unit count, text discarded' names a specific operation (counting UTF-16 units) but does not specify which of the 9 parameters is the input text. It is not a tautology, but it fails to establish the resource or parameter being acted upon, leaving the tool's exact purpose ambiguous.

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. It does not mention any conditions, exclusions, or alternative tools, leaving the agent without any basis for selection.

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