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

The description explicitly says 'Query discarded,' which discloses a meaningful side-effect trait—input is not persisted—and implies a read-only length computation. However, it does not explain behavior when multiple parameters are provided or describe what the returned length looks like, and no annotations exist to fill that gap.

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 only two sentences, with the action front-loaded and the side-effect statement following directly. Every word earns its place, though its brevity contributes to the ambiguity elsewhere.

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?

With nine optional parameters, no output schema, and no annotations, the two-sentence description is insufficient. It does not explain the role of the extra parameters, the return format, or what happens if multiple properties are supplied, making the tool hard to invoke confidently.

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 description coverage is 100%, so the baseline is 3. The phrase 'search query' aligns with the `query` property description ('Search text; discarded after the length check'), adding slight meaning. But the description fails to address the other eight parameters or specify which one carries the search query, leaving potential for misuse.

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 ('Count') and resource ('characters in a search query'), which clearly differentiates it from sibling counting tools like memory-key-count or hn-front-count. However, the nine-parameter schema creates ambiguity about which input actually represents the search query, so it is not perfectly precise.

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, nor any conditions, prerequisites, or exclusions. The description simply states what it does, leaving the agent to infer the appropriate context from the tool name.

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