Cooper Email

List custom domains

cooper_list_domains

Read-onlyIdempotent

Use this when you need the custom domains on the signed-in account, including DNS status. Read-only; requires auth; no inputs. Returns {object:"list", data:[{id, domain, status, status_detail, mail, records, warnings, dns}]}. Each record has status valid, missing, or invalid, found from the last check, and hint (null, or {code, message, found_at} saying what to change). warnings is an empty array when none. existing_mail_provider means this hostname already has MX at another provider. Custom domains are included on Starter (15) and Pro (200). Free includes 1. Past that cap is HTTP 402 plan_limit_exceeded. Publish exactly the records returned, with their host, type, value, priority for MX, and ttl. The receiving MX hostname and the DKIM value come from that response. Do not invent them. dns.mode automatic means Cooper wrote the records in an active Cloudflare zone it already controls. dns.mode external means you publish them at your DNS host. Cooper does not register a domain, create a zone, or move nameservers. Keep one SPF TXT with a single include; an existing SPF is merged into it. A DMARC p=reject record is left as published and blocks mail until DKIM for that domain verifies. mail.receiving and mail.sending stay false until the matching records verify. Then POST /api/v1/inboxes with domain creates username@domain. Failure codes: unauthorized.

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`data`	No	Items on this page, in the order the tool description gives.
`object`	No	Object type name, such as list, message, or thread.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedNov 3, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "description": "Custom domains on the account.",
+  "properties": {
+    "data": {
+      "description": "Items on this page, in the order the tool description gives.",
+      "items": {
+        "properties": {
+          "created_at": {
+            "description": "ISO-8601 time the object was created."
+          },
+          "dns": {
+            "description": "{mode}: automatic when Cooper wrote the records, external when you publish them."
+          },
+          "domain": {
+            "description": "Hostname of the custom domain."
+          },
+          "id": {
+            "description": "Domain id (dom_…). Pass it as domain_id to cooper_verify_domain."
+          },
+          "idempotent": {
+            "description": "True when this result replays an earlier request with the same key instead of acting again."
+          },
+          "mail": {
+            "description": "{receiving, sending, inboxes} flags. Each turns true once its records verify."
+          },
+          "notices": {
+            "description": "Usage notices, such as [{type: limit_warning, resource, used, limit, upgrade_url}] at 80 percent of a plan limit."
+          },
+          "records": {
+            "description": "DNS records to publish [{host, type, value, priority, ttl, status, found, hint}]. Publish exactly these."
+          },
+          "status": {
+            "description": "pending until DNS matches, then verified."
+          },
+          "status_detail": {
+            "description": "Plain-language note on what is still pending."
+          },
+          "warnings": {
+            "description": "Problems found in existing DNS, such as existing_mail_provider. Empty when none."
+          }
+        },
+        "type": "object"
+      }
+    },
+    "object": {
+      "description": "Object type name, such as list, message, or thread."
+    }
+  },
+  "type": "object"
+}

AddedOct 8, 2026

TDQS

A4.2/5.0

Behavior5/5

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

Annotations already declare readOnlyHint and idempotentHint, yet the description still adds substantial context beyond them: auth requirement, no inputs, plan caps (Starter 15 / Pro 200 / Free 1), the HTTP 402 plan_limit_exceeded failure, and the unauthorized failure code. It also explains downstream behaviours (mail.receiving/sending stay false until records verify, DMARC p=reject blocking mail) that materially affect how results should be interpreted.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The purpose and scoping sentence is correctly front-loaded, but the bulk of the text is DNS-setup instructions for other operations: how to publish records, SPF merging, dns.mode semantics, and POST /api/v1/inboxes to create an inbox. That is useful context but not this tool's job, and it dilutes the definition considerably.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite an output schema being present, the description adds the field semantics the schema cannot convey: the valid/missing/invalid status meanings, the hint object shape, warnings as an empty array when none, and what existing_mail_provider signals. For a zero-parameter read tool this is as complete as an agent needs.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so there is nothing for the description to disambiguate, and the declared 'no inputs' matches the empty schema. Baseline for a zero-parameter tool applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Opens with a specific verb and resource: reads the custom domains on the signed-in account, including DNS status. It does not explicitly distinguish itself from the neighbouring cooper_add_domain or cooper_verify_domain, but the scope ('signed-in account', no inputs) is unambiguous enough to separate it from per-domain tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Use this when you need the custom domains on the signed-in account' gives a clear trigger condition, and the later plan-cap/402 note tells the agent what failure to expect. It never states when NOT to use it, e.g. use cooper_get_inbox instead when you want inbox-level detail, so it falls short of full routing guidance.

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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