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

The description adds a useful behavioral detail: 'Query discarded' indicates the input is not retained or used beyond the count. However, with no annotations, it does not cover other behavioral aspects such as return format, errors, or whether any external service is involved.

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 action and followed by a useful behavioral note. There is no filler or repetition; every word earns its place.

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 pure-count tool, this is nearly complete: the relevant parameter is identifiable from the schema, and 'Count characters' makes the output obvious even without an output schema. The main gap is that the description does not explicitly say only the query parameter is used despite the other optional parameters present.

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 each parameter is already documented. The description maps the purpose to the 'query' parameter but adds no parameter-level detail beyond what the schema already provides.

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') and a resource ('a search query'), so it is clear what the tool does. It does not explicitly differentiate from sibling tools, but the resource and tool name are specific enough for selection.

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 intended use is implied: call this when a character count for search text is needed. There is no explicit when-not-to-use guidance or reference to alternative tools, but the purpose itself provides reasonable context.

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