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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that: it names the returned fields (declared identity, behaviour class, signals, reasons, mismatch flag) and the 500-event cap, so the agent knows what the analysis produces. It does not explain what happens with very sparse event lists, which keeps it short of a 5.

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?

Three tight sentences, front-loaded with the action and its output classes, followed by input constraints. Nothing is repeated and the length matches the tool's complexity.

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?

There is no output schema, so the description carries the full burden of explaining return values, and it does so by listing identity, behaviour class, signals, reasons and the mismatch flag. Combined with the event-cap constraint, an agent has everything needed to invoke the tool and interpret its result.

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 coverage is already 100%, and every nested event field carries its own description, so the baseline is 3. The description still adds meaning beyond the schema by clarifying that all event fields are optional and that the caller should send whatever its server actually parsed, which tells an agent how lenient it can be when constructing input.

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 gives a specific verb and resource ('Classify one visitor from its requests') and immediately enumerates the output classes (acts-on-results, agent-tool-use, agent-message, probe, indexer, web-scanner, web). That enumeration lets an agent distinguish this tool from the sibling list_known_bots and identify_client without opening any schema.

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 context is implied by the 'one visitor' scope and the event-input instruction ('send what your server parsed'), but the description never states when to prefer this tool over identify_client, nor any exclusions or prerequisites. Guidance is adequate but remains inferential.

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