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

The description states 'Query discarded' indicating the input is not retained, but it does not clarify whether the tool performs any network calls or has side effects, especially given the many unrelated 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 a single, concise sentence that front-loads the action ('Count characters') and then notes the disposal of the query. It is efficient and well-structured.

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?

The description does not explain why the schema includes eight unrelated parameters when the tool's purpose is to count characters in a search query; this omission could confuse an agent. It also does not mention return format, but that is less critical.

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 already provides descriptions for all parameters, including 'query' as 'Search text; discarded after the length check'. The description adds no additional meaning beyond the schema, and the purpose of the other eight parameters is unclear.

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 clearly states the tool counts characters in a search query, which distinguishes it from sibling tools that count other things (e.g., hn-front-count, memory-key-count).

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?

The description gives no indication of when to use this tool versus alternatives; it does not mention any competing tools or conditions for selection.

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