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

The phrase 'Query discarded' discloses that the input is not persisted, but the description omits other behavioral aspects such as read-only nature, network access, or side effects. The schema descriptions also suggest discarding for other parameters, but the tool description only addresses the query.

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 a single, concise sentence that directly conveys the tool's purpose without 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?

The description lacks essential context about the tool's behavior with the extra schema parameters, the expected output format, or error conditions. Without an output schema, the user is left guessing what the tool returns (e.g., just a number?). This incompleteness is amplified by the mismatch between the narrow description and the broad parameter list.

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 description only mentions the 'query' parameter, while the schema includes eight additional parameters (ref, url, city, feed, host, json, path, zone) with generic descriptions like 'discarded after the shape check.' The description does not clarify how these relate to the tool's purpose or whether they are ignored, leaving their meaning ambiguous.

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 the tool's function: 'Count characters in a search query.' It specifies a precise action (count) and a resource (search query), distinguishing it from sibling tools that handle URLs, timezones, or validation.

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 guidance on when to use this tool versus alternatives. It does not mention scenarios, prerequisites, or contrast with sibling tools like 'normalize-url' or 'validate-json'.

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