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

With no annotations provided, the description carries the full burden. It discloses that the query is discarded, which is a useful behavioral trait. However, it does not mention whether the tool performs any I/O, returns a number, or has side effects. For a simple counter, this is minimal but not entirely absent.

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 two short sentences with zero fluff. The main action is front-loaded, and the 'Query discarded' note adds value without waste. It is appropriately sized for a simple tool.

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 no output schema and no annotations, the description should at least indicate the return format (e.g., a character count). It also lacks usage guidance. While the schema covers parameters, the description is incomplete for an agent to fully understand the tool's purpose and output.

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 cover 100% of parameters, including 'query' explicitly stating 'Search text; discarded after the length check.' The description adds no additional meaning beyond the schema, which meets the baseline for full coverage.

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 and resource: 'Count characters in a search query.' This distinguishes it from sibling tools like 'hn-front-count' (count front page items) and 'memory-key-count' (count memory keys). The addition 'Query discarded' clarifies the non-persistent nature, but the return value is not stated.

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 provides no guidance on when to use this tool versus alternatives. It does not mention any context, exclusions, or preferability over sibling tools. The agent is left to infer usage from the name and schema.

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