List sender addresses available for a connected account to choose the correct From address when sending email.
List sender addresses available for an account.
| Name | Required | Description | Default |
|---|---|---|---|
| accountId | No | Account to operate on. Optional when exactly one account is connected. |
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes |
Changes observed during successful MCP inspections.
v0.11.1Output schema / $schemaRemoved value: -"http://json-schema.org/draft-07/schema#"v0.11.0Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "data": {
+ "items": {
+ "additionalProperties": true,
+ "properties": {
+ "email": {
+ "type": "string"
+ },
+ "isPrimary": {
+ "type": "boolean"
+ },
+ "source": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "email",
+ "isPrimary",
+ "source"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ }
+ },
+ "required": [
+ "data"
+ ],
+ "type": "object"
+}v0.9.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description's burden is reduced. It adds one useful scoping fact (results are tied to an account), but says nothing about ordering, emptiness, or whether the list is cached/dynamic.
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?
One short, front-loaded sentence with no filler or redundancy. Nothing to trim and nothing buried.
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?
For a zero-argument-required read tool with an output schema that covers the return shape, the description is close to sufficient. It still omits why an agent would need the list (e.g., picking a valid From address) and any note about result volume, leaving a modest gap for a multi-account mail workflow.
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% and the single accountId parameter is fully documented in the schema, including the 'optional when exactly one account is connected' rule. The description's 'for an account' phrasing merely echoes that, so the 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?
The description uses a clear verb+resource pair ('List sender addresses') and scopes it to an account, so an agent immediately knows what it returns. It does not need to differentiate from siblings since no other tool in the list deals with send-as identities, but it also doesn't say so explicitly.
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?
Usage is only implied: the agent can infer this is the tool to call before choosing a sender address for send_email, but the description never states when to use it or references a related tool such as send_email or preview_send. No exclusions or prerequisites are given.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.