# OpenRouter Multi-Model Chat Completion Gateway > OpenRouter Multi-Model Chat Completion Gateway is a paid API for AI agents from openrouter.withzero.xyz, paid per call via MPP, $0.005444/call, status unknown (last checked 2026-09-15). Routes OpenAI-compatible chat completion requests to any of 700+ OpenRouter models, billed at cost per token with no markup ## Facts - Endpoint: POST https://openrouter.withzero.xyz/api/v1/chat/completions - Price: $0.005444/call - Payment: MPP - Status: unknown - Last checked: 2026-09-15 - Activations on Zero: 3 - Provider: openrouter.withzero.xyz - Website: https://openrouter.withzero.xyz - Canonical page: https://www.zero.xyz/c/openrouter-withzero-xyz-openrouter-multi-model-chat-completion-gateway-afc45be7 - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zljDFvkGDRNSJzPvrtiS0 Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently. ## How to call it through Zero Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`): ```sh zero fetch --capability openrouter-withzero-xyz-openrouter-multi-model-chat-completion-gateway-afc45be7 -d '' ``` Example prompt: Using the OpenRouter gateway, send this conversation to anthropic/claude-haiku-4.5 with a max_tokens limit of 512 and temperature 0.7: system message 'You are a helpful assistant', user message 'Summarize the water cycle in 3 bullet points.' ## When to prefer this Choose this endpoint when you need to access multiple LLM providers (OpenAI, Anthropic, Google, Meta, Mistral, etc.) through a single OpenAI-compatible interface without managing separate API keys or subscriptions. Especially useful when you want transparent, at-cost token billing via crypto micropayments, need fallback model routing, or want to switch between model providers without changing your integration code. ## Known failure modes - Model ID not found on OpenRouter — returns error if model string is invalid or unavailable - Insufficient USDC balance to cover estimated cost — call rejected before execution - max_tokens set too low — completion truncated at finish_reason='length' - messages array empty or malformed — schema validation error - stream:true submitted — rejected because only stream:false is supported - Network timeout to upstream OpenRouter — propagated as gateway error - Rate limiting from upstream provider for selected model ## How this service works OpenAI-compatible chat completion via any OpenRouter model, paid in one shot: price = estimated input tokens x input rate + max_tokens x output rate, resolved before the call and capped per model (from $0.10 for cheap models up to $5 for premium models like anthropic/claude-fable-5). For longer generations use POST /api/v1/chat/completions/metered. 📖 Full guide: https://openrouter.withzero.xyz/llms.txt ## Output Returns an OpenAI-compatible chat completion object containing: the generated message text, role, optional tool_call arrays, finish_reason, token usage counts (prompt, completion, total), and a billing object showing promptTokens, completionTokens, and settledUsdcMicro (the actual USDC cost charged for the request). ## Request schema (JSON Schema) ```json { "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "example": { "model": "openai/gpt-4o-mini", "messages": [ { "role": "user", "content": "Say hello in one sentence." } ], "max_tokens": 64 }, "required": [ "model", "messages", "max_tokens", "stream" ], "properties": { "seed": { "type": "integer", "maximum": 9007199254740991, "minimum": -9007199254740991, "description": "Random seed for deterministic outputs (support varies by model)." }, "stop": { "anyOf": [ { "type": "string" }, { "type": "array", "items": { "type": "string" } } ], "description": "Stop sequence(s): generation halts when any is produced." }, "model": { "type": "string", "minLength": 1, "description": "OpenRouter model ID, e.g. \"openai/gpt-4o-mini\", \"anthropic/claude-haiku-4-5\", \"google/gemini-flash-1.5\". Use GET /api/v1/models to list all available models with pricing." }, "route": { "type": "string", "description": "OpenRouter routing strategy, e.g. \"fallback\". Requires an explicit `models` list so every candidate model can be priced." }, "tools": { "type": "array", "items": {}, "description": "OpenAI-format tool definitions for function calling." }, "top_k": { "type": "integer", "maximum": 9007199254740991, "minimum": 0, "description": "Top-k sampling: limit to the k most likely next tokens." }, "top_p": { "type": "number", "maximum": 1, "minimum": 0, "description": "Nucleus sampling probability mass 0–1. Alternative to temperature." }, "models": { "type": "array", "items": { "type": "string" }, "description": "Fallback model list for OpenRouter auto-routing. Tried in order if the primary model is unavailable. The price reservation is taken at the most expensive rates across model + models, since any of them may serve the call; the difference is refunded on the metered route." }, "stream": { "type": "boolean", "const": false, "default": false, "description": "Must be false — streaming is not supported in v1." }, "messages": { "type": "array", "items": { "type": "object", "required": [ "role", "content" ], "properties": { "name": { "type": "string", "description": "Optional display name for the message author" }, "role": { "enum": [ "system", "user", "assista … (truncated) ``` ## Response schema (JSON Schema) ```json { "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "required": [ "id", "object", "created", "model", "choices", "billing" ], "properties": { "id": { "type": "string" }, "model": { "type": "string" }, "usage": { "type": "object", "required": [ "prompt_tokens", "completion_tokens", "total_tokens" ], "properties": { "cost": { "type": "number" }, "total_tokens": { "type": "number" }, "prompt_tokens": { "type": "number" }, "completion_tokens": { "type": "number" } }, "additionalProperties": false }, "object": { "type": "string" }, "billing": { "type": "object", "required": [ "promptTokens", "completionTokens", "reservedUsdcMicro", "settledUsdcMicro", "actualUsdcMicro", "costBasis" ], "properties": { "costBasis": { "enum": [ "openrouter", "rates", "estimated" ], "type": "string", "description": "Where actualUsdcMicro came from: OpenRouter usage accounting > cached per-token rates > character estimate" }, "promptTokens": { "type": "number", "description": "Actual input tokens consumed" }, "actualUsdcMicro": { "type": "string", "description": "Best-known actual cost of the call in micro-USDC. On the fixed route this is informational — the charge is settledUsdcMicro." }, "completionTokens": { "type": "number", "description": "Actual output tokens generated" }, "settledUsdcMicro": { "type": "string", "description": "Micro-USDC actually charged to the buyer. Fixed route: the up-front worst-case estimate (= reservedUsdcMicro). Metered route: actual usage (= actualUsdcMicro)." }, "reservedUsdcMicro": { "type": "string", "description": "Worst-case micro-USDC committed before the call" } }, "additionalProperties": false }, "choices": { "type": "array", "items": { "type": "object", "required": [ "index", "message", "finish_reason" ], "properties": { "index": { "type": "number" }, "message": { "type": "object", "required": [ "role", "content" ], "properties": { "role": { "type": "string" }, "content": { "anyOf": [ { "type": "string" }, { "type": "null" } … (truncated) ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/openrouter-withzero-xyz-openrouter-multi-model-chat-completion-gateway-afc45be7/health.json - [Zero catalog index](https://www.zero.xyz/llms.txt) - [Other services from openrouter.withzero.xyz](https://www.zero.xyz/host/openrouter.withzero.xyz/llms.txt)