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

The 'Query discarded' sentence is a useful behavioral disclosure, especially with no annotations present to indicate side effects or persistence. However, the description does not explicitly state that the operation is read-only or what the return behavior is, so the behavioral burden is only partially carried.

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?

Two short sentences, front-loaded with the purpose, with a non-redundant behavioral note. There is no filler, repetition, or unnecessary detail.

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 counting utility with a fully documented input schema, the description is nearly sufficient for invocation. The main gap is the lack of an explicit return value/type, but 'Count characters' makes an integer count the natural inference. The discard behavior is also clearly stated.

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 met without additional parameter explanation in the tool description. The description aligns with the 'query' parameter but adds no meaning beyond what the schema already provides. Other parameters are already individually documented as discarded or checked.

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 operation: counting characters in a search query, and adds that the query is discarded. This goes beyond a tautology and conveys the core function. It does not explicitly differentiate itself from sibling count/shape tools, but 'search query' narrows the resource enough to be mostly clear.

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 on when to use this tool versus alternatives such as memory-key-count, hn-front-count, or the URL/shape validation tools. The description implies a general use case but provides no exclusions, prerequisites, or alternative routing, leaving the agent to infer applicability.

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