> ## Documentation Index > Fetch the complete documentation index at: https://docs.rumik.ai/llms.txt > Use this file to discover all available pages before exploring further. # create a variable > declare a `{name}` with its default value. variables are account-wide: every agent whose prompt or greeting spells `{name}` reads the same row. connect a `before_call` tool with `toolId` (and pick one of its `outputs` with `toolOutput`) to fill the value at the start of each call; the default is used when the tool fails. ## OpenAPI ````yaml /openapi.json post /v1/variables openapi: 3.1.0 info: title: silk api version: 1.0.0 description: >- rumik ai's speech api. synthesize speech with the expressive `muga` model, the faster `mulberry` model or the multilingual `mulberry-1.6` model over http or a streaming websocket session, run conversational voice agents over webrtc, a realtime pcm socket or the phone, and manage everything the agents playground does — agents, voices, variables, tools, phone numbers, sip trunks and outbound calls — with the same api key. contact: name: rumik ai url: https://rumik.ai servers: - url: https://silk-api.rumik.ai description: production security: - bearerAuth: [] tags: - name: speech description: text-to-speech over HTTP and WebSocket. - name: voice agents description: start calls with a deployed agent from your own app. - name: agents description: build, configure, deploy and inspect your agents. - name: calls description: place outbound phone calls and read call history. - name: voices description: the voices, languages and styles an agent may use. - name: variables description: account-wide `{name}` prompt variables and their defaults. - name: tools description: HTTP tools agents call before or during a call. - name: phone numbers description: 'numbers rented through rumik: search, rent, connect, release.' - name: sip trunks description: bring your own numbers over SIP. paths: /v1/variables: post: tags: - variables summary: create a variable description: >- declare a `{name}` with its default value. variables are account-wide: every agent whose prompt or greeting spells `{name}` reads the same row. connect a `before_call` tool with `toolId` (and pick one of its `outputs` with `toolOutput`) to fill the value at the start of each call; the default is used when the tool fails. operationId: createVariable requestBody: content: application/json: schema: $ref: '#/components/schemas/VariableCreateRequest' examples: default: value: name: company defaultValue: acme required: true responses: '201': description: created. content: application/json: schema: $ref: '#/components/schemas/Variable' examples: default: value: id: 019f9f43-5e71-7082-bd9e-0f1a2b3c4d5e name: company defaultValue: acme toolId: null toolOutput: null createdAt: '2026-09-11T10:00:00Z' updatedAt: '2026-09-11T10:00:00Z' '401': description: >- `unauthorized` — key missing, malformed, unknown, revoked or expired. content: application/json: schema: $ref: '#/components/schemas/Error' examples: unauthorized: value: error: Invalid API key code: unauthorized '403': description: '`forbidden_scope` — the key was created without the `agent` scope.' content: application/json: schema: $ref: '#/components/schemas/Error' examples: forbidden_scope: value: error: This API key lacks the 'agent' scope code: forbidden_scope '409': description: >- `agent_variable_name_taken` — another variable already has this name (case-insensitive). `agent_variable_limit_exceeded` — the account already has 200 variables. content: application/json: schema: $ref: '#/components/schemas/Error' examples: agent_variable_name_taken: value: error: A variable with this name already exists code: agent_variable_name_taken agent_variable_limit_exceeded: value: error: You've reached the limit of variables for this account code: agent_variable_limit_exceeded '422': description: >- `agent_variable_invalid` — the tool named is not one of the account's before-call tools, or the output pick does not exist on it. `invalid_request` — a field is missing or malformed. `details` lists every failing field. content: application/json: schema: $ref: '#/components/schemas/Error' examples: agent_variable_invalid: value: error: The variable is invalid code: agent_variable_invalid invalid_request: value: error: >- body.toNumber: must be an E.164 phone number, e.g. +14155551234 code: invalid_request details: - loc: body.toNumber message: must be an E.164 phone number, e.g. +14155551234 '429': description: >- `rate_limited` — the key's per-minute budget is spent. `Retry-After` says how long to wait; the body carries `limit` and `current`. content: application/json: schema: $ref: '#/components/schemas/Error' examples: rate_limited: value: error: Rate limit exceeded code: rate_limited limit: 100 current: 101 headers: Retry-After: description: seconds to wait before retrying (per-key rate limit only). schema: type: integer components: schemas: VariableCreateRequest: properties: name: type: string maxLength: 64 description: >- `^[A-Za-z][A-Za-z0-9_]*$`, up to 64 characters, unique on the account (case-insensitive). used as `{name}` in prompts. defaultValue: type: string maxLength: 2000 default: '' description: >- the value when no tool supplies one (up to 2000 characters). blank by default. toolId: anyOf: - type: string format: uuid - type: 'null' description: >- a `before_call` tool that fills this variable at the start of every call. toolOutput: anyOf: - type: string maxLength: 65 - type: 'null' description: >- which of that tool's `outputs` to take (its bare name). omit for a tool with one output, or one named like the variable. type: object required: - name title: VariableCreateRequest description: '``POST /agents/variables``: the same shape, nothing optional about it.' Variable: properties: id: type: string format: uuid description: the variable's id. name: type: string description: the `{name}` prompts use. defaultValue: type: string description: the fallback value. toolId: anyOf: - type: string format: uuid - type: 'null' description: the before-call tool feeding it, or null. toolOutput: anyOf: - type: string - type: 'null' description: the output taken from that tool, or null. createdAt: type: string format: date-time updatedAt: type: string format: date-time type: object required: - id - name - defaultValue - toolId - toolOutput - createdAt - updatedAt title: Variable description: an account-wide `{name}` prompt variable. Error: type: object properties: error: type: string description: human-readable error message. code: type: string description: machine-readable error code. securitySchemes: bearerAuth: type: http scheme: bearer description: >- your rumik api key, e.g. `rk_live_...`. create one in the rumik dashboard. ````