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

With no annotations, the description carries the full behavioral burden. 'Query discarded' explicitly discloses the main side effect — the query is not retained after the call. For a stateless length-check tool, this is meaningful transparency, even if auth/network details are not relevant.

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 with the core action front-loaded and no filler. Every word earns its place, making it easy for an agent to parse quickly.

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 simple and the schema covers parameters, but there is no explicit statement of the return value (e.g., integer character count) and no guidance about ignoring the non-query fields. Without an output schema, the description should make the returned count more explicit.

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 schema fully documents all nine optional parameters. The description reinforces that the relevant input is a search query, but it does not add meaningful detail beyond the schema or clarify that the other eight fields are decoys/ignored.

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 and resource: 'Count characters in a search query.' This clearly distinguishes it from sibling tools that normalize URLs, validate JSON, check file paths, or fetch statuses. The added 'Query discarded' also signals that this is not a search or storage operation.

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?

Usage is implied rather than stated: an agent would call this tool when it needs the character length of a search query. There is no explicit when-to-use/when-not-to-use guidance, nor any mention of alternative sibling tools for similar tasks.

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