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

With absolutely no annotations, the description carries the behavioral burden. It does add the meaningful disclosure 'Query discarded', telling the agent that the input is not persisted. However, it does not mention what the tool returns, whether it is idempotent/safe, or how it treats the other optional schema parameters, leaving gaps for a description with no annotations.

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 filler. 'Count characters in a search query.' states purpose, and 'Query discarded.' adds a meaningful behavioral detail. Every sentence 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?

The tool is a simple operation, but the context is under-specified: there is no output schema, no annotations, no required parameters, and 9 optional input properties. The description does not explicitly tell the caller which property to pass ('query') nor what the call returns (likely a numeric character length). An agent selecting and invoking this tool correctly would need to infer a lot from the property name alone.

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 description paraphrases the 'query' parameter by talking about a 'search query' but does not add additional meaning, such as clarifying that 'query' is the sole input consumers should provide or that the other eight params are ignored. The schema already describes each property well.

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 clearly states a specific operation: 'Count characters in a search query.' It identifies both the action and the resource, making the tool's purpose immediately obvious. This also distinguishes it from sibling count/shape tools such as memory-key-count and domain-shape.

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 indication of when to use this tool versus alternatives, nor does it mention why an agent should choose 'search-query-len' over a generic length or validation tool. Usage is only implied by the tool's name and the stated action.

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