List supported languages, built-in voices with preview URLs, owned voice clones and your clone limit.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Output schema / anyOfPrevious value: -[
- {
- "additionalProperties": {},
- "properties": {
- "languages": {
- "items": {
- "additionalProperties": {},
- "propertyNames": {
- "type": "string"
- },
- "type": "object"
- },
- "type": "array"
- },
- "limit": {
- "type": "number"
- },
- "operation_id": {
- "type": "string"
- },
- "regions": {
- "items": {
- "additionalProperties": {},
- "propertyNames": {
- "type": "string"
- },
- "type": "object"
- },
- "type": "array"
- },
- "voices": {
- "items": {
- "additionalProperties": {},
- "propertyNames": {
- "type": "string"
- },
- "type": "object"
- },
- "type": "array"
- }
- },
- "required": [
- "languages",
- "regions",
- "voices",
- "limit"
- ],
- "type": "object"
- },
- {
- "additionalProperties": {},
- "properties": {
- "error": {
- "type": "string"
- },
- "message": {
- "type": "string"
- }
- },
- "required": [
- "error"
- ],
- "type": "object"
- },
- {
- "additionalProperties": {},
- "properties": {
- "message": {
- "type": "string"
- },
- "next_action": {
- "type": "string"
- },
- "operation_id": {
- "type": "string"
- },
- "status": {
- "type": "string"
- }
- },
- "required": [
- "operation_id",
- "status"
- ],
- "type": "object"
- }
-]New value: +[
+ {
+ "additionalProperties": {},
+ "properties": {
+ "languages": {
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "label": {
+ "type": "string"
+ },
+ "locale": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "locale",
+ "label"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ },
+ "limit": {
+ "maximum": 9007199254740991,
+ "minimum": 0,
+ "type": "integer"
+ },
+ "operation_id": {
+ "type": "string"
+ },
+ "regions": {
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "label": {
+ "type": "string"
+ },
+ "locale": {
+ "type": "string"
+ },
+ "voices": {
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "gender": {
+ "enum": [
+ "female",
+ "male",
+ "neutral"
+ ],
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "nativeLocale": {
+ "type": "string"
+ },
+ "provider_voice_id": {
+ "description": "Provider voice ID used when assigning a built-in voice to an agent.",
+ "maxLength": 200,
+ "minLength": 1,
+ "type": "string"
+ },
+ "sample": {
+ "format": "uri",
+ "type": "string"
+ }
+ },
+ "required": [
+ "provider_voice_id",
+ "label",
+ "gender"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ }
+ },
+ "required": [
+ "locale",
+ "label",
+ "voices"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ },
+ "voices": {
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "created_at": {
+ "format": "date-time",
+ "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))T(?:(?:[01]\\d|2[0-3]):[0-5]\\d:[0-5]\\d(?:\\.\\d+)?(?:Z))$",
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "provider_voice_id": {
+ "anyOf": [
+ {
+ "maxLength": 200,
+ "minLength": 1,
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+ ],
+ "description": "Provider ID for preview and agent assignment once the clone is ready and the account is entitled."
+ },
+ "status": {
+ "enum": [
+ "creating",
+ "ready",
+ "verification_required",
+ "failed",
+ "deleting"
+ ],
+ "type": "string"
+ },
+ "voice_id": {
+ "description": "Patch clone ID for renaming, deleting or checking verification.",
+ "maxLength": 200,
+ "minLength": 1,
+ "type": "string"
+ }
+ },
+ "required": [
+ "voice_id",
+ "provider_voice_id",
+ "label",
+ "status",
+ "created_at"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ }
+ },
+ "required": [
+ "languages",
+ "regions",
+ "voices",
+ "limit"
+ ],
+ "type": "object"
+ },
+ {
+ "additionalProperties": {},
+ "properties": {
+ "error": {
+ "type": "string"
+ },
+ "message": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "error"
+ ],
+ "type": "object"
+ },
+ {
+ "additionalProperties": {},
+ "properties": {
+ "message": {
+ "type": "string"
+ },
+ "next_action": {
+ "type": "string"
+ },
+ "operation_id": {
+ "type": "string"
+ },
+ "status": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "operation_id",
+ "status"
+ ],
+ "type": "object"
+ }
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds only the shape of the payload (languages, preview URLs, clones, limit), which duplicates what the output schema likely conveys. No mention of auth scope, pagination, or whether preview URLs expire.
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 sentence, no filler, and the most important noun (supported languages/voices) is front-loaded. Every clause corresponds to a distinct part of the return value.
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?
With an output schema present, the description need not explain return values, and with zero parameters there is nothing else to document. The only gap is that it never says the results are scoped to the authenticated account, which the phrase 'owned voice clones and your clone limit' only hints at.
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?
The tool takes zero parameters, so the baseline is 4; nothing in the description could add parameter meaning. The schema is fully closed (additionalProperties: false) and requires nothing.
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?
Specific verb 'List' with four enumerated resources: languages, built-in voices with preview URLs, owned clones, and clone limit. An agent can distinguish it from create_voice/delete_voice/get_voice_preview. It stops short of naming a sibling it is not, so it lands at 4 rather than 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?
Usage is only implied by the verb and the enumerated contents; there is no statement of when to call this versus get_voice_preview or verify_voice, and no prerequisite (e.g. account scope) is given. An agent can infer 'call this to discover available voices' but must do the inference itself.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.