list_domainsList sending domains for this account.
| Name | Required | Description | Default |
|---|---|---|---|
| limit | No | Page size (1–100) | |
| cursor | No | Opaque cursor for the next page | |
| inbound_enabled | No | Only domains with inbound receiving on (or off) |
| Name | Required | Description | Default |
|---|---|---|---|
| domains | Yes | Sending domains | |
| has_more | No | True when another page follows | |
| next_cursor | No | Pass as cursor for the next page; null on the last page |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "domains": {
+ "description": "Sending domains",
+ "items": {
+ "properties": {
+ "click_tracking": {
+ "type": "boolean"
+ },
+ "created_at": {
+ "description": "ISO 8601",
+ "type": "string"
+ },
+ "id": {
+ "description": "Domain id",
+ "type": "string"
+ },
+ "inbound_enabled": {
+ "type": "boolean"
+ },
+ "inbound_error": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "inbound_status": {
+ "description": "disabled, pending, active, or error",
+ "type": "string"
+ },
+ "name": {
+ "description": "Domain name",
+ "type": "string"
+ },
+ "open_tracking": {
+ "type": "boolean"
+ },
+ "status": {
+ "description": "Verification status",
+ "type": "string"
+ },
+ "tls_mode": {
+ "type": "string"
+ },
+ "verified_at": {
+ "description": "ISO 8601",
+ "type": [
+ "string",
+ "null"
+ ]
+ }
+ },
+ "required": [
+ "id",
+ "name"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ },
+ "has_more": {
+ "description": "True when another page follows",
+ "type": "boolean"
+ },
+ "next_cursor": {
+ "description": "Pass as cursor for the next page; null on the last page",
+ "type": [
+ "string",
+ "null"
+ ]
+ }
+ },
+ "required": [
+ "domains"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered without description help. The description adds only the account-scoping fact; it says nothing about pagination behavior or result size limits, which would be the useful extra context given the cursor parameter.
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?
A single short sentence with no filler and the resource stated up front. It is efficient, though arguably too terse for a paginated list tool.
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?
An output schema exists, so return values need not be explained, and all parameters are documented in the schema. What is missing is any acknowledgement of paging behavior or the relationship to domain-management siblings, leaving the definition minimally viable.
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 all three parameters (limit, cursor, inbound_enabled) are already fully documented in the schema. The description adds no parameter-level detail, which makes the baseline 3 appropriate.
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 verb+resource ('List sending domains') scoped to 'this account', which is enough to distinguish it from get_domain and create_domain by inference. However, it never explicitly contrasts itself with those siblings, so an agent must rely on the naming convention rather than the text.
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?
There is no statement of when to use this tool versus get_domain (single domain) or list_emails, and no mention of pagination workflow despite the cursor parameter. Usage is only implied by the verb 'List'.
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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