list_send_asList the sender addresses available for a mailbox.
| 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.
Output schema / (root)Previous value: -nullNew value: +{
+ "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"
+}Input schema / properties / accountId / anyOfPrevious value: -[
- {
- "minLength": 1,
- "type": "string"
- },
- {
- "type": "null"
- }
-]New value: +[
+ {
+ "maxLength": 512,
+ "minLength": 1,
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+]Input schema / $schemaPrevious value: -"https://json-schema.org/draft/2020-12/schema"New value: +"http://json-schema.org/draft-07/schema#"Input schema / properties / accountId / anyOfAdded value: +[
+ {
+ "minLength": 1,
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+]Input schema / properties / accountId / descriptionAdded value: +"Account to operate on. Optional when exactly one account is connected."Input schema / properties / accountId / maxLengthRemoved value: -512Input schema / properties / accountId / minLengthRemoved value: -1Input schema / properties / accountId / typeRemoved value: -"string"Input schema / $schemaPrevious value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"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 fully covered. The description adds only the mailbox scoping context and says nothing about ordering, pagination, or whether addresses are verified — modest value on top of the 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?
A single front-loaded sentence with no filler, which is appropriately sized for a one-parameter read tool. It is efficient but borders on under-specified rather than maximally informative.
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?
The output schema exists and annotations cover safety, so the description need not explain returns; for a simple read-only list tool the stated purpose is nearly sufficient. The only real gap is the absence of usage context linking it to the send flow.
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?
With a single parameter and 100% schema description coverage ('Account to operate on. Optional when exactly one account is connected.'), the schema already carries the semantics. The description adds no further meaning about accountId or its null/default behavior, so 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?
States a specific verb ('List') and resource ('sender addresses available for a mailbox'), which is clearly distinct from list_accounts or list_labels by resource noun. It stops short of explicitly contrasting with the closest sibling (list_accounts), so a 4 rather than a 5.
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?
The description gives no when-to-use or when-not-to-use guidance and never names an alternative. An agent must infer that this is the pre-flight lookup before send_email or preview_send; nothing is stated.
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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