Read one owned number by number_id; omit it to inspect the default outbound number. Accepts calls:read or numbers:read. Number-management settings, revision, recovery deadline and workspace_revision require numbers:read. Does not place a call or expose agent instructions or voices.
| Name | Required | Description | Default |
|---|---|---|---|
| number_id | No |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Input schema / properties / number_idAdded value: +{
+ "maxLength": 200,
+ "minLength": 1,
+ "type": "string"
+}Output schema / anyOfPrevious value: -[
- {
- "additionalProperties": {},
- "properties": {
- "caller_id_status": {
- "description": "Caller ID verification state.",
- "enum": [
- "verified",
- "unverified"
- ],
- "type": "string"
- },
- "phone_number": {
- "description": "Authenticated account caller ID in E.164 format.",
- "type": "string"
- }
- },
- "required": [
- "phone_number",
- "caller_id_status"
- ],
- "type": "object"
- },
- {
- "additionalProperties": {},
- "properties": {
- "error": {
- "description": "Machine-readable failure code.",
- "type": "string"
- },
- "message": {
- "description": "Explanation or recovery guidance.",
- "type": "string"
- }
- },
- "required": [
- "error"
- ],
- "type": "object"
- },
- {
- "additionalProperties": {},
- "properties": {
- "next_action": {
- "type": "string"
- },
- "operation_id": {
- "type": "string"
- },
- "status": {
- "type": "string"
- }
- },
- "required": [
- "operation_id",
- "status"
- ],
- "type": "object"
- }
-]New value: +[
+ {
+ "additionalProperties": {},
+ "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"
+ },
+ "operation_id": {
+ "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"
+ },
+ "workspace_revision": {
+ "description": "Included only with numbers:read; use when changing the default number.",
+ "maximum": 9007199254740991,
+ "minimum": 0,
+ "type": "integer"
+ }
+ },
+ "required": [
+ "number_id",
+ "phone_number",
+ "label",
+ "kind",
+ "state",
+ "caller_id_status",
+ "inbound_enabled",
+ "outbound_enabled",
+ "inbound_configured",
+ "outbound_configured",
+ "is_default"
+ ],
+ "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 / descriptionRemoved value: -"Successful result or a machine-readable tool error."Output schema / anyOfPrevious value: -[
- {
- "additionalProperties": {},
- "properties": {
- "caller_id_status": {
- "description": "Caller ID verification state.",
- "enum": [
- "verified",
- "unverified"
- ],
- "type": "string"
- },
- "phone_number": {
- "description": "Authenticated account caller ID in E.164 format.",
- "type": "string"
- }
- },
- "required": [
- "phone_number",
- "caller_id_status"
- ],
- "type": "object"
- },
- {
- "additionalProperties": {},
- "properties": {
- "error": {
- "description": "Machine-readable failure code.",
- "type": "string"
- },
- "message": {
- "description": "Explanation or recovery guidance.",
- "type": "string"
- }
- },
- "required": [
- "error"
- ],
- "type": "object"
- }
-]New value: +[
+ {
+ "additionalProperties": {},
+ "properties": {
+ "caller_id_status": {
+ "description": "Caller ID verification state.",
+ "enum": [
+ "verified",
+ "unverified"
+ ],
+ "type": "string"
+ },
+ "phone_number": {
+ "description": "Authenticated account caller ID in E.164 format.",
+ "type": "string"
+ }
+ },
+ "required": [
+ "phone_number",
+ "caller_id_status"
+ ],
+ "type": "object"
+ },
+ {
+ "additionalProperties": {},
+ "properties": {
+ "error": {
+ "description": "Machine-readable failure code.",
+ "type": "string"
+ },
+ "message": {
+ "description": "Explanation or recovery guidance.",
+ "type": "string"
+ }
+ },
+ "required": [
+ "error"
+ ],
+ "type": "object"
+ },
+ {
+ "additionalProperties": {},
+ "properties": {
+ "next_action": {
+ "type": "string"
+ },
+ "operation_id": {
+ "type": "string"
+ },
+ "status": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "operation_id",
+ "status"
+ ],
+ "type": "object"
+ }
+]Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "anyOf": [
+ {
+ "additionalProperties": {},
+ "properties": {
+ "caller_id_status": {
+ "description": "Caller ID verification state.",
+ "enum": [
+ "verified",
+ "unverified"
+ ],
+ "type": "string"
+ },
+ "phone_number": {
+ "description": "Authenticated account caller ID in E.164 format.",
+ "type": "string"
+ }
+ },
+ "required": [
+ "phone_number",
+ "caller_id_status"
+ ],
+ "type": "object"
+ },
+ {
+ "additionalProperties": {},
+ "properties": {
+ "error": {
+ "description": "Machine-readable failure code.",
+ "type": "string"
+ },
+ "message": {
+ "description": "Explanation or recovery guidance.",
+ "type": "string"
+ }
+ },
+ "required": [
+ "error"
+ ],
+ "type": "object"
+ }
+ ],
+ "description": "Successful result or a machine-readable tool error.",
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description goes further by disclosing required auth scopes ('calls:read or numbers:read') and which fields need the stricter numbers:read scope. It also sets boundaries on what the response will not contain.
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 dense sentences with zero filler, front-loading the core operation and the optional-parameter behavior. Auth and negative-scope details follow in a logical order.
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?
An output schema exists, so return-value documentation is unnecessary. With a single optional parameter, the description covers selection behavior, auth requirements, and scope boundaries — everything an agent needs to invoke it correctly.
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 description coverage is 0%, so the description must carry the semantics — and it does, explaining that number_id selects a specific owned number and that omitting it returns the default outbound number. It stops short of stating accepted formats or whether unknown IDs error.
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 ('Read one owned number') plus the key scoping behavior (omit number_id to get the default outbound number). This clearly separates it from list_phone_numbers and search_phone_numbers, which return multiple records.
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?
Gives a concrete usage rule (pass number_id for a specific number, omit it for the default outbound number) and useful exclusions ('Does not place a call or expose agent instructions or voices'). It does not explicitly name the sibling tools it competes with, which keeps it just short of a 5.
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.