> ## 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. # start a web call > start a voice-agent call and return the credentials a browser joins it with over webrtc. media flows browser ↔ agent directly. two ways in: `agentId` with an api key that has the `agent` scope starts the call in one hop — the call id is minted inside this request, so the agent's before-call tools receive it as `{call_id}` before you see it in the response. `accessToken` from `/v1/register-call` starts the call under the `call_id` that response already gave you, needs no api key, and is what to use when a before-call tool has to recognise the id, or when the page starts the call itself. either way the agent must be deployed and the returned `callId` identifies the call in conversations and usage. ## OpenAPI ````yaml /openapi.json post /v1/webcall 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/webcall: post: tags: - voice agents summary: start a web call description: >- start a voice-agent call and return the credentials a browser joins it with over webrtc. media flows browser ↔ agent directly. two ways in: `agentId` with an api key that has the `agent` scope starts the call in one hop — the call id is minted inside this request, so the agent's before-call tools receive it as `{call_id}` before you see it in the response. `accessToken` from `/v1/register-call` starts the call under the `call_id` that response already gave you, needs no api key, and is what to use when a before-call tool has to recognise the id, or when the page starts the call itself. either way the agent must be deployed and the returned `callId` identifies the call in conversations and usage. operationId: startWebCall requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/WebCallRequest' examples: default: summary: one hop, with your api key value: agentId: ua_fe3277d8 registered: summary: a registered call, no api key value: accessToken: wct_9f8c2b1e4d5a4e6fa7b8c9d0e1f2a3b4 responses: '200': description: the call started; join with these credentials. content: application/json: schema: $ref: '#/components/schemas/WebCallResponse' '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/PaymentRequired' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/AgentNotFound' '409': $ref: '#/components/responses/AgentNotDeployed' '422': $ref: '#/components/responses/ValidationError' '429': $ref: '#/components/responses/CapacityOrRateLimited' '502': $ref: '#/components/responses/AgentStartFailed' '503': $ref: '#/components/responses/Unavailable' security: - bearerAuth: [] - {} components: schemas: WebCallRequest: type: object description: exactly one of `agentId` or `accessToken`. oneOf: - required: - agentId - required: - accessToken properties: agentId: type: string example: ua_fe3277d8 description: >- the agent to run — its uuid or its `ua_…` handle. `agent_id` is accepted too. needs your api key in `Authorization`. accessToken: type: string example: wct_9f8c2b1e4d5a4e6fa7b8c9d0e1f2a3b4 description: >- the single-use `wct_` token from `/v1/register-call`. it is the credential on its own — no api key — and the call starts under that response's `call_id`. `access_token` is accepted too. WebCallResponse: type: object properties: token: type: string description: short-lived livekit access token for the browser to join with. host: type: string example: wss://livekit.rumik.ai description: livekit websocket url to connect to. roomName: type: string example: call-891e23fe503944c28dbf5e5a2a105190 description: the room created for this call. callId: type: string format: uuid description: >- the call id, as shown in conversations and usage, and what your tools receive as `{call_id}`. for a registered call it is the `call_id` register-call already gave you. Error: type: object properties: error: type: string description: human-readable error message. code: type: string description: machine-readable error code. ConcurrencyLimitExceeded: type: object required: - error - code - active_requests - limit properties: error: type: string example: >- silk is already processing 2 requests for this account. try again when one finishes, or increase your plan capacity. code: type: string const: concurrency_limit_exceeded active_requests: type: integer minimum: 0 example: 2 limit: type: integer minimum: 1 example: 2 responses: Unauthorized: description: bearer token missing, invalid, or expired. content: application/json: schema: $ref: '#/components/schemas/Error' PaymentRequired: description: >- the account cannot fund the call (`insufficient_balance`), or is paused after a failed payment (`access_blocked`). content: application/json: schema: $ref: '#/components/schemas/Error' Forbidden: description: key revoked or account disabled. content: application/json: schema: $ref: '#/components/schemas/Error' AgentNotFound: description: no such agent on this account. content: application/json: schema: $ref: '#/components/schemas/Error' AgentNotDeployed: description: >- the agent exists but has never been deployed, so no version is live to run. content: application/json: schema: $ref: '#/components/schemas/Error' ValidationError: description: validation failed. check the error field. content: application/json: schema: $ref: '#/components/schemas/Error' CapacityOrRateLimited: description: >- either a per-key rate limit or account-wide concurrent-request capacity was reached. headers: Retry-After: description: >- present for a rate-limit response; capacity failures do not include it. schema: type: integer content: application/json: schema: oneOf: - $ref: '#/components/schemas/Error' - $ref: '#/components/schemas/ConcurrencyLimitExceeded' AgentStartFailed: description: the agent could not be started. safe to retry. content: application/json: schema: $ref: '#/components/schemas/Error' Unavailable: description: upstream temporarily unavailable. retry shortly. content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: bearerAuth: type: http scheme: bearer description: >- your rumik api key, e.g. `rk_live_...`. create one in the rumik dashboard. ````