registrable_domainDomain + nearest suffix (the "site").
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| input | Yes | Canonical form of the input domain | |
| registrable_domain | Yes | Registrable domain (site), null if none |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "domain": "www.example.com"
+ },
+ {
+ "domain": "blog.github.io"
+ }
+]Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "input": {
+ "description": "Canonical form of the input domain",
+ "type": "string"
+ },
+ "registrable_domain": {
+ "description": "Registrable domain (site), null if none",
+ "type": [
+ "string",
+ "null"
+ ]
+ }
+ },
+ "required": [
+ "input",
+ "registrable_domain"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. The description adds no behavioral details such as what 'nearest suffix' means or how the tool processes domains, failing to add value beyond annotations.
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 very concise (one sentence), but conciseness sacrifices clarity. It is adequately sized but lacks essential information.
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?
Given the existence of an output schema, the tool still lacks explanation of what it returns. The single parameter and sibling relationships are not addressed, leaving the description incomplete.
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 schema has 0% description coverage for the 'domain' parameter. The description's phrase 'Domain + nearest suffix' does not clarify expected format or usage, offering minimal added meaning.
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 'Domain + nearest suffix (the "site")' is cryptic and does not clearly state that the tool extracts the registrable domain from a given domain name. It lacks a specific verb and resource, making it vague.
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?
No guidance is provided on when to use this tool versus siblings like 'public_suffix' or others. There is no context on scenarios or exclusion criteria.
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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