Sendmux Email Inbox API + Sending

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Get Sending Connection

sending_get_connection

Read-onlyIdempotent

Validate the current sending credential and retrieve its team, connection label, and permissions. Use this to confirm email.send access before initiating outbound operations.

Instructions

Validate the current Sending credential and read its team, connection label and permissions. Requires email.send. This does not send email or check credits or provider readiness.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`If-None-Match`	No	Weak ETag from a previous response. When it matches the current resource, the server returns 304 Not Modified with no body.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv1.0.8Sep 15, 2026

addedOutput schema / $schema

Added value: +"https://json-schema.org/draft/2020-12/schema"

removedOutput schema / additionalProperties
```
Removed value: -true
```

addedOutput schema / properties

Added value: +{
+  "result": {
+    "allOf": [
+      {
+        "properties": {
+          "meta": {
+            "additionalProperties": false,
+            "properties": {
+              "request_id": {
+                "description": "Unique request identifier",
+                "example": "req_clxxxxxxxxxxxxxxxxxxxxxxxxx",
+                "type": "string"
+              }
+            },
+            "required": [
+              "request_id"
+            ],
+            "type": "object"
+          },
+          "ok": {
+            "enum": [
+              true
+            ],
+            "type": "boolean"
+          }
+        },
+        "required": [
+          "ok",
+          "meta"
+        ],
+        "type": "object"
+      },
+      {
+        "properties": {
+          "data": {
+            "additionalProperties": false,
+            "properties": {
+              "credential": {
+                "additionalProperties": false,
+                "properties": {
+                  "id": {
+                    "type": "string"
+                  },
+                  "name": {
+                    "type": [
+                      "string",
+                      "null"
+                    ]
+                  },
+                  "type": {
+                    "enum": [
+                      "api_key",
+                      "oauth",
+                      "agent_token"
+                    ],
+                    "example": "api_key",
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "id",
+                  "type",
+                  "name"
+                ],
+                "type": "object"
+              },
+              "label": {
+                "description": "Display label for this connection.",
+                "type": "string"
+              },
+              "mailboxes": {
+                "items": {
+                  "additionalProperties": false,
+                  "properties": {
+                    "email": {
+                      "format": "email",
+                      "type": "string"
+                    },
+                    "id": {
+                      "type": "string"
+                    }
+                  },
+                  "required": [
+                    "id",
+                    "email"
+                  ],
+                  "type": "object"
+                },
+                "type": "array"
+              },
+              "permissions": {
+                "items": {
+                  "type": "string"
+                },
+                "type": "array"
+              },
+              "team": {
+                "additionalProperties": false,
+                "properties": {
+                  "id": {
+                    "type": "string"
+                  },
+                  "name": {
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "id",
+                  "name"
+                ],
+                "type": "object"
+              }
+            },
+            "required": [
+              "team",
+              "credential",
+              "label",
+              "permissions",
+              "mailboxes"
+            ],
+            "type": "object"
+          }
+        },
+        "required": [
+          "data"
+        ],
+        "type": "object"
+      }
+    ],
+    "unevaluatedProperties": {
+      "not": {}
+    },
+    "x-fastmcp-top-level-schema": "ConnectionResponse"
+  }
+}

addedOutput schema / required
```
Added value: +[
+  "result"
+]
```

Addedv1.0.3Sep 8, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds the authorization requirement (email.send) and the boundary exclusions (does not send email or check credits/provider readiness), which are valuable behavioral details not captured in annotations. No contradiction with annotations.

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

Conciseness5/5

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

The description is two sentences: the first states the primary action and output, the second adds the permission requirement and explicitly lists what the tool does not do. Every sentence carries meaning, and the most important information is front-loaded. No redundancy or fluff.

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

Completeness4/5

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

Given the tool's simplicity (one optional parameter, no required params) and the presence of an output schema (which would describe the returned team, connection label, and permissions), the description is sufficiently complete. It covers purpose, permission, and exclusions. The only minor gap is not describing the behavior when the credential is invalid, but that is likely covered by the output schema.

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

Parameters3/5

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

Schema coverage is 100% because the only parameter, If-None-Match, has a description explaining its purpose (weak ETag, 304 response). The tool description adds no additional parameter details, but since the schema already fully documents it, the baseline of 3 is appropriate. The description could have noted how the ETag affects the response, but it is not required.

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

Purpose5/5

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

The description clearly states the tool validates the Sending credential and reads its team, connection label, and permissions. It uses specific verbs (validate, read) and names the resource. It also explicitly distinguishes itself by noting it does not send email or check credits/provider readiness, which separates it from sibling sending 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?

The description states the prerequisite of email.send permission and clarifies what the tool does not do (send email, check credits, provider readiness), implicitly guiding the agent away from using it for those purposes. However, it does not explicitly name alternative tools like sending_send_email or mailbox_get_connection, leaving some inference required.

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