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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds meaningful behavioral context about overlap/containment semantics and operator-based lookup, but does not disclose return format, pagination, or error behavior. That is consistent with the calibration example where annotations cover the safety profile and the description adds contextual value.

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 leads with a full JSON-RPC invocation for a sibling tool, which is verbose and arguably tangential to lookup_prefix's own behavior. The remainder is efficient and packs function, use cases, and alternative input into a compact passage, but the bulky beginning prevents a higher score.

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 tool with only two optional parameters and no output schema, the description adequately explains input modes, output semantics (every containing/contained/overlapping prefix), and an example. Minor gaps—such as no explicit statement about mutual exclusivity or behavior when both parameters are omitted—are acceptable given the low complexity and strong annotations.

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 adds value by signaling that the parameters are alternatives ('Give an operator or source slug instead'), implying mutual exclusivity that the schema properties do not state. It also reinforces with a concrete example, though the schema already includes one.

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 precise verb+resource: 'get every published operator prefix that contains it, is contained by it, or partially overlaps it.' It also names the two input modes (CIDR or operator/source slug) and gives concrete use cases, making the tool's purpose unmistakable and distinct from siblings like no_arguments_report_the_crawler_ip_ranges_this_host_mirrors.

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 clear contextual usage: it is 'the check for does my network collide with a crawler range' and for 'auditing an allowlist.' It also directs when to use the operator slug instead of a CIDR. However, it does not explicitly compare against siblings like range_stats or verify_batch, so it lacks explicit exclusions.

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