IPv4/IPv6 CIDR subnet calculator: network, netmask, wildcard, broadcast, first/last usable host, total and usable addresses, block type. Optional split lists the smaller subnets (e.g. the /64s in a /48).
| Name | Required | Description | Default |
|---|---|---|---|
| cidr | Yes | e.g. 192.168.1.0/24 or 2001:db8::/48 | |
| split | No | Optional: split into subnets of this prefix length, e.g. 26 or 64 (first 64 listed plus the total count) |
Changes observed during successful MCP inspections.
Input schema / properties / splitAdded value: +{
+ "description": "Optional: split into subnets of this prefix length, e.g. 26 or 64 (first 64 listed plus the total count)",
+ "type": "integer"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It faithfully lists the computed return fields and discloses the split truncation rule ('first 64 listed plus the total count'), which is useful. However, it does not state that this is a pure local computation with no network calls, nor how invalid or malformed CIDR input is handled.
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 sentences, front-loaded with the core capability and appended with the optional behavior. Every clause carries distinct information with no filler.
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's enumeration of returned fields is exactly the right compensation. Combined with the schema's parameter examples, an agent has enough to invoke it correctly; only error/edge-case behavior for invalid CIDRs is missing.
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 100%, so both parameters are already documented with examples in the schema. The description only re-illustrates the split use case ('the /64s in a /48') without adding semantics the schema lacks, so baseline 3 applies.
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?
Names a specific resource (IPv4/IPv6 CIDR) and operation (subnet calculation), then enumerates exactly what it computes: network, netmask, wildcard, broadcast, first/last host, totals, block type. This is clearly distinguishable from the sibling lookup/validation tools (validate_ip, lookup_ip, batch_lookup_ip), which resolve addresses rather than compute subnet math.
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 purpose implies usage (you have a CIDR and want its derived fields), and the split option is illustrated with a concrete case ('the /64s in a /48'). But there is no explicit statement of when to prefer this over validate_ip or lookup_ip, and no exclusions or error conditions mentioned.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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