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

With no annotations, the description carries the full burden of behavioral disclosure. It explicitly states 'Query discarded', implying the tool does not retain input and has no side effects. This adds transparency but does not mention whether the operation is read-only, any error conditions, or what happens with remote calls. The 'discarded' note is useful but the description lacks detail on edge cases and output format.

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 no redundancy. It front-loads the action ('Count characters') and then a key behavioral note ('Query discarded'). Every sentence earns its place, and the information is immediately clear.

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 simple tool with 9 optional parameters and no output schema, the description is mostly adequate for the core function. It clearly states the primary action, but it does not explicitly define the return value (e.g., an integer count) or address potential edge cases like empty strings or invalid input. Given its simplicity, a 3 is reasonable; it is not severely incomplete but leaves some ambiguity about 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 has 100% coverage for all 9 parameters, each with descriptive text. The description adds no additional parameter meaning beyond what the schema already provides; it only highlights the 'query' parameter. Since schema coverage is high, the baseline is 3, and the description does not compensate with extra detail, so a 3 is appropriate.

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 action ('Count characters') on a specific resource ('a search query'), which clearly conveys what the tool does. However, it does not mention what the tool returns (e.g., an integer length) and it does not differentiate from siblings like 'hn-front-count' or 'memory-key-count' which also count. The mention of 'search query' helps distinguish, so this is above adequate but not fully distinct.

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?

There is no guidance about when to use this tool versus alternatives. The description does not indicate conditions for use, prerequisites, or situations where a sibling tool would be preferable. The agent receives no context about selection criteria, so this dimension is weak.

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