List this account's phone numbers, active direction availability and default_number_id. Use number_id to select a source for place_call. Accepts calls:read or numbers:read; management settings and workspace_revision are included only with numbers:read. Does not expose agent instructions or voices.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Input schema / $schemaAdded value: +"http://json-schema.org/draft-07/schema#"Output schema / $schemaAdded value: +"http://json-schema.org/draft-07/schema#"Output schema / anyOfPrevious value: -[
- {
- "properties": {
- "default_source_number_id": {
- "type": [
- "string",
- "null"
- ]
- },
- "phone_numbers": {
- "items": {
- "type": "object"
- },
- "type": "array"
- }
- },
- "required": [
- "default_source_number_id",
- "phone_numbers"
- ],
- "type": "object"
- },
- {
- "properties": {
- "error": {
- "type": "string"
- },
- "message": {
- "type": "string"
- }
- },
- "required": [
- "error"
- ],
- "type": "object"
- }
-]New value: +[
+ {
+ "additionalProperties": {},
+ "properties": {
+ "default_number_id": {
+ "anyOf": [
+ {
+ "maxLength": 200,
+ "minLength": 1,
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+ ]
+ },
+ "operation_id": {
+ "type": "string"
+ },
+ "phone_numbers": {
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "caller_id_status": {
+ "enum": [
+ "verified",
+ "unverified"
+ ],
+ "type": "string"
+ },
+ "inbound_configured": {
+ "type": "boolean"
+ },
+ "inbound_enabled": {
+ "type": "boolean"
+ },
+ "is_default": {
+ "type": "boolean"
+ },
+ "kind": {
+ "enum": [
+ "caller",
+ "owned"
+ ],
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "number_id": {
+ "maxLength": 200,
+ "minLength": 1,
+ "type": "string"
+ },
+ "outbound_configured": {
+ "type": "boolean"
+ },
+ "outbound_enabled": {
+ "type": "boolean"
+ },
+ "phone_number": {
+ "type": "string"
+ },
+ "settings": {
+ "additionalProperties": false,
+ "description": "Number-management settings, included only with numbers:read permission.",
+ "properties": {
+ "country": {
+ "type": "string"
+ },
+ "release_at": {
+ "anyOf": [
+ {
+ "format": "date-time",
+ "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))T(?:(?:[01]\\d|2[0-3]):[0-5]\\d:[0-5]\\d(?:\\.\\d+)?(?:Z))$",
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+ ]
+ },
+ "retained": {
+ "type": "boolean"
+ },
+ "revision": {
+ "maximum": 9007199254740991,
+ "minimum": 0,
+ "type": "integer"
+ }
+ },
+ "required": [
+ "country",
+ "revision",
+ "retained",
+ "release_at"
+ ],
+ "type": "object"
+ },
+ "state": {
+ "enum": [
+ "provisioning",
+ "requirements",
+ "active",
+ "suspended",
+ "release_pending",
+ "released",
+ "failed"
+ ],
+ "type": "string"
+ }
+ },
+ "required": [
+ "number_id",
+ "phone_number",
+ "label",
+ "kind",
+ "state",
+ "caller_id_status",
+ "inbound_enabled",
+ "outbound_enabled",
+ "inbound_configured",
+ "outbound_configured",
+ "is_default"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ },
+ "workspace_revision": {
+ "description": "Included only with numbers:read; use when changing the default number.",
+ "maximum": 9007199254740991,
+ "minimum": 0,
+ "type": "integer"
+ }
+ },
+ "required": [
+ "default_number_id",
+ "phone_numbers"
+ ],
+ "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"
+ }
+]Output schema / (root)Previous value: -nullNew value: +{
+ "anyOf": [
+ {
+ "properties": {
+ "default_source_number_id": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "phone_numbers": {
+ "items": {
+ "type": "object"
+ },
+ "type": "array"
+ }
+ },
+ "required": [
+ "default_source_number_id",
+ "phone_numbers"
+ ],
+ "type": "object"
+ },
+ {
+ "properties": {
+ "error": {
+ "type": "string"
+ },
+ "message": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "error"
+ ],
+ "type": "object"
+ }
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real value by naming the two accepted scopes and stating that management settings and workspace_revision appear only with numbers:read. The explicit exclusion ('Does not expose agent instructions or voices') further prevents a false expectation about the payload.
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?
Three short sentences, front-loaded with what is listed, then scoping/auth, then exclusions. No filler; every clause carries a distinct constraint or use case.
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 zero parameters, rich annotations, and an output schema, the description covers the remaining agent-relevant unknowns: required scopes, scope-dependent content, and what is deliberately omitted. Nothing needed to call it correctly is missing.
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, which is the baseline-4 case. The mention of number_id is about place_call, not this tool's input, so it adds navigation context rather than parameter semantics, but it does not mislead about inputs.
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 and resource ('List this account's phone numbers') plus the concrete fields returned (direction availability, default_number_id). It doesn't differentiate from the close sibling search_phone_numbers or get_phone_number, which is the only thing keeping it from 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?
It provides one concrete downstream usage hint ('Use number_id to select a source for place_call') and explains scope-conditional output, which implies when the tool is useful. However, there is no explicit when-to-use-this-vs-search_phone_numbers guidance or exclusion statement.
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.