> ## Documentation Index > Fetch the complete documentation index at: https://docs.slng.ai/llms.txt > Use this file to discover all available pages before exploring further. # Create a response (OpenAI Responses protocol) > Route an OpenAI Responses request. Uses `input` and `instructions`; returns an `output` array. Additional Responses fields pass through. ## OpenAPI ````yaml /api-reference/context-router/context-router.oas.yaml post /responses openapi: 3.1.0 info: title: Context Router API version: 1.0.0 summary: >- OpenAI-compatible chat endpoints with routing, response caching and per-call templating. description: > Routes OpenAI-compatible requests to a configured model and returns the standard OpenAI response. Two endpoints share the same auth, routing, caching and templating: * `POST /chat/completions` - Chat Completions protocol. Recommended. * `POST /responses` - Responses protocol. SLNG request extensions: `template_variables`, `slng_config`, `slng_agent_id`, `slng_session_id`, `slng_analytics`, `slng_pure_proxy`. Response headers: `x-slng-request-id`, `x-slng-response-source`, `x-slng-model`. servers: - url: https://{region}.context-router.slng.ai/v1 description: Regional base URL. Pick the region closest to your callers. variables: region: default: india enum: - india - us - indonesia description: Deployment region. Other regions may exist. security: - SlngApiKey: [] tags: - name: Chat description: OpenAI Chat Completions surface. - name: Responses description: OpenAI Responses-compatible endpoint. paths: /responses: post: tags: - Responses summary: Create a response (OpenAI Responses protocol) description: > Route an OpenAI Responses request. Uses `input` and `instructions`; returns an `output` array. Additional Responses fields pass through. operationId: createResponse parameters: - $ref: '#/components/parameters/XSlngAgentId' - $ref: '#/components/parameters/XSlngSessionId' - $ref: '#/components/parameters/XSlngRequestId' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/ResponsesRequest' responses: '200': description: A Responses-protocol envelope. headers: x-slng-request-id: $ref: '#/components/headers/XSlngRequestIdResponse' x-slng-response-source: $ref: '#/components/headers/XSlngResponseSource' x-slng-model: $ref: '#/components/headers/XSlngModel' content: application/json: schema: $ref: '#/components/schemas/ResponsesResponse' '400': description: Bad request. Same error codes as `/chat/completions`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '422': description: Unprocessable request. Same error codes as `/chat/completions`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' components: parameters: XSlngAgentId: name: X-Slng-Agent-Id in: header required: false description: > Stable agent ID. Scopes the cache — change it when the system prompt changes. Required unless sent as `slng_agent_id` (body wins). Max 256 chars; no whitespace, commas, pipes or braces. schema: $ref: '#/components/schemas/SlngId' example: clinic-scheduler-v1 XSlngSessionId: name: X-Slng-Session-Id in: header required: false description: | ID for a single call, constant across its turns. Required unless sent as `slng_session_id` (body wins). Same character rules as the agent ID. schema: $ref: '#/components/schemas/SlngId' example: call-8f2c1a4e-9b07-4d3a-a1e2-7c5f0d6b2a11 XSlngRequestId: name: X-Slng-Request-Id in: header required: false description: > Optional correlation ID, echoed back in `x-slng-request-id`. `X-Request-Id` is also accepted. schema: type: string schemas: ResponsesRequest: type: object additionalProperties: true description: > OpenAI Responses body (`input` and `instructions`), plus the same SLNG extensions as Chat Completions. properties: model: type: string default: slng/auto input: description: Responses-protocol input. oneOf: - type: string - type: array items: type: object additionalProperties: true instructions: type: string stream: type: boolean template_variables: $ref: '#/components/schemas/TemplateVariables' slng_config: $ref: '#/components/schemas/SlngConfig' slng_agent_id: $ref: '#/components/schemas/SlngId' slng_session_id: $ref: '#/components/schemas/SlngId' slng_analytics: type: boolean default: false slng_pure_proxy: type: boolean default: false ResponsesResponse: type: object additionalProperties: true description: OpenAI Responses-compatible `output` envelope. properties: id: type: string object: type: string model: type: string output: type: array items: type: object additionalProperties: true usage: type: object additionalProperties: true ErrorResponse: type: object required: - error properties: error: type: object properties: message: type: string type: type: string example: invalid_request_error param: type: - string - 'null' code: type: string enum: - missing_client_id - invalid_client_id - missing_template_variables - invalid_slng_config description: > Error code. `slng_config` failures other than a non-object body return a 400 with a message beginning `invalid slng_config:`. SlngId: type: string maxLength: 256 pattern: ^[^\s,|{}]+$ description: | Opaque ID. Max 256 characters; no whitespace, commas, pipes or braces. TemplateVariables: type: object maxProperties: 64 description: > SLNG extension. `{name: value}` map substituted into `{{name}}` placeholders in the **system message only**. Names are letters, digits and underscore. Limits (over any returns 422): 64 variables, 64-char names, 4000-char values. A `{{name}}` with no value returns 422 (`missing_template_variables`); unused variables are ignored. Use for personalization that is spoken or echoed. Values that steer the answer (language, plan, region) belong in the prompt — steering here can make the cache serve another caller's answer. propertyNames: pattern: ^[A-Za-z0-9_]{1,64}$ additionalProperties: type: string maxLength: 4000 example: caller_name: Rajesh city: Mumbai SlngConfig: type: object required: - tiers additionalProperties: false description: > SLNG extension. Model endpoints and provider keys sent inline, replacing your saved configuration for that request. Treat as a credential (HTTPS, keep out of logs); under 256 KB serialized. Invalid config returns 400 (`invalid slng_config:`); a non-object returns 422 (`invalid_slng_config`). properties: tiers: type: object description: > Up to three tiers (`"1"`, `"2"`, `"3"`) tried in order. Within a tier, traffic splits by `weight` (summing to 100). A failed model (5xx, timeout, 429) retries once against the next option. propertyNames: enum: - '1' - '2' - '3' additionalProperties: type: array minItems: 1 items: $ref: '#/components/schemas/SlngConfigEntry' SlngConfigEntry: type: object required: - model - weight - endpoint additionalProperties: false properties: model: type: string description: > Label for this entry. Pass it as the request `model` to target it directly. weight: type: integer minimum: 1 maximum: 100 description: Share of the tier's traffic; weights in a tier sum to 100. endpoint: $ref: '#/components/schemas/SlngEndpoint' SlngEndpoint: type: object additionalProperties: false description: > Where the model is served, with its credentials. Required fields depend on `provider`; fields for another provider are rejected. properties: provider: type: string default: openai-compat enum: - openai-compat - openai-responses - azure - vertex - bedrock description: > `openai-compat` (default) for any OpenAI Chat Completions service (OpenAI, Groq, vLLM, and so on). `openai-responses` calls the upstream Responses API instead — for models that only work that way, typically reasoning models that refuse tools. url: type: string format: uri description: > Required for `openai-compat`, `openai-responses` and `azure`. For `azure`, the resource **root** (`https://my-resource.cognitiveservices.azure.com/`), not the deployment URL. api_key: type: string description: > Required for `openai-compat`, `openai-responses` and `azure`. Your provider key, not your SLNG key. auth_header: type: string description: > Optional (`openai-compat`). Custom key header, for example `x-goog-api-key` for Gemini. model_id: type: string description: > Model name sent to the provider when it differs from the `model` label. Required for `bedrock`. azure_deployment: type: string description: 'Required for `provider: azure`. The Azure deployment name.' api_version: type: string description: 'Required for `provider: azure`, for example `2024-12-01-preview`.' vertex_credentials: type: object additionalProperties: true description: > Required for `provider: vertex`. GCP service-account key as a JSON object. vertex_location: type: string description: 'Required for `provider: vertex`. The Vertex AI location.' vertex_project: type: string description: > Optional for `provider: vertex`. Defaults to the service-account key's project. aws_access_key_id: type: string description: 'Required for `provider: bedrock`.' aws_secret_access_key: type: string description: 'Required for `provider: bedrock`.' aws_region: type: string description: 'Required for `provider: bedrock`.' aws_session_token: type: string description: 'Optional for `provider: bedrock`, for temporary credentials.' examples: - url: https://api.openai.com/v1 api_key: sk-... - provider: azure url: https://my-resource.cognitiveservices.azure.com/ api_key: ... azure_deployment: gpt-4o-deploy api_version: 2024-12-01-preview - provider: bedrock aws_access_key_id: AKIA... aws_secret_access_key: ... aws_region: ap-south-1 model_id: anthropic.claude-3-5-sonnet-20241022-v2:0 headers: XSlngRequestIdResponse: description: > The router's ID for this request, on every response. Quote it in support requests. schema: type: string XSlngResponseSource: description: > Answer source: `llm` (live model) or `cache`. `router` and `analytics` appear only with those features. schema: type: string enum: - llm - cache - router - analytics XSlngModel: description: > The model that produced the answer, after any failover. Live answers only. schema: type: string securitySchemes: SlngApiKey: type: http scheme: bearer description: > Send your SLNG API key as a Bearer token (an OpenAI SDK's `api_key` option). Provider credentials in `slng_config` authenticate to those providers. ````