Gemini Native Format

Generate Content (Gemini Format)

post

Generates content using Google's native Gemini API format. This is a drop-in replacement for Google's generateContent endpoint — simply replace generativelanguage.googleapis.com with api.fastrouter.ai in your base URL and use your FastRouter API key.

Full URL: POST https://api.fastrouter.ai/v1/models/{model}:generateContent?key=YOUR_FASTROUTER_API_KEY

Authentication: Pass your FastRouter API key via the ?key=YOUR_API_KEY query parameter (Google Gemini style).

Request/Response format: Identical to Google's Gemini API. The request body uses contents (with parts) and generationConfig. The response includes candidates with generated content and usageMetadata with token counts.

Cost tracking: The response usageMetadata object includes a cost field showing credits consumed.

Authorizations

keyQuery

keystringRequired

FastRouter API Key (Gemini style). Get yours at https://fastrouter.ai

Format: ?key=YOUR_API_KEY

Path parameters

modelstringRequired

The Gemini model ID to use (e.g. gemini-2.5-pro, gemini-2.5-flash).

Example: gemini-2.5-pro

Query parameters

keystringRequired

FastRouter API key (Gemini style: pass as query parameter).

Body

application/json

Responses

200

Successful response with generated content.

application/json

modelVersionstringOptional

400

Bad Request - The request is malformed. This could be due to missing parameters, invalid formats, or routing errors.

Note: the 400 body shape is not uniform. Validation errors return the structured object below, but routing/model errors may instead return a plain string: { "error": "<message>" }. A few endpoints (e.g. some file operations) may return a plain-text body rather than JSON.

application/json

401

Invalid Credentials - Your API key is invalid, missing, or disabled. Check your credentials.

Note: the 401 error body uses code, message, param, and type (there is no status field), and type is invalid_request_error.

application/json

402

Insufficient Credits - Your account or API key has run out of credits. Add more credits and retry the request.

application/json

429

Rate Limited - You have exceeded your request limits (TPM/RPM). Slow down or increase your limits.

application/json

500

Internal Error - Something went wrong on our side. Retry the request, and contact support if the issue persists.

application/json

502

Bad Gateway — failed to reach Google AI Studio.

application/json

post/v1/models/{model}:generateContent

HTTPcURLJavaScriptPython

POST /v1/models/{model}:generateContent?key=text HTTP/1.1
Host: api.fastrouter.ai
Content-Type: application/json
Accept: */*
Content-Length: 154

{
  "contents": [
    {
      "role": "user",
      "parts": [
        {
          "text": "Explain how AI works in a few sentences."
        }
      ]
    }
  ],
  "generationConfig": {
    "temperature": 0.7,
    "maxOutputTokens": 1024
  }
}

{
  "candidates": [
    {
      "content": {
        "parts": [
          {
            "text": "text"
          }
        ],
        "role": "text"
      },
      "finishReason": "text",
      "safetyRatings": [
        {
          "category": "text",
          "probability": "text"
        }
      ]
    }
  ],
  "usageMetadata": {
    "promptTokenCount": 1,
    "candidatesTokenCount": 1,
    "totalTokenCount": 1,
    "cost": 1
  },
  "modelVersion": "text"
}

Stream Generate Content (Gemini Format)

post

Generates content using Google's native Gemini API format with streaming. Returns Server-Sent Events (SSE) with incremental content chunks. This is a drop-in replacement for Google's streamGenerateContent endpoint.

Full URL: POST https://api.fastrouter.ai/v1/models/{model}:streamGenerateContent?key=YOUR_FASTROUTER_API_KEY

Authentication: Pass your FastRouter API key via the ?key=YOUR_API_KEY query parameter (Google Gemini style).

Streaming format: Returns SSE events with data: prefixed JSON objects. Each chunk contains partial candidates with generated content. The final chunk includes usageMetadata with token counts and a cost field.

Cost tracking: The final streamed chunk's usageMetadata object includes a cost field showing credits consumed.

Authorizations

keyQuery

keystringRequired

FastRouter API Key (Gemini style). Get yours at https://fastrouter.ai

Format: ?key=YOUR_API_KEY

Path parameters

modelstringRequired

The Gemini model ID to use (e.g. gemini-2.5-pro, gemini-2.5-flash).

Example: gemini-2.5-pro

Query parameters

keystringRequired

FastRouter API key (Gemini style: pass as query parameter).

Body

application/json

Responses

200

Streaming response with Server-Sent Events containing generated content chunks.

text/event-stream

Each SSE event contains a JSON object with partial candidates and usage metadata.

400

Bad Request - The request is malformed. This could be due to missing parameters, invalid formats, or routing errors.

Note: the 400 body shape is not uniform. Validation errors return the structured object below, but routing/model errors may instead return a plain string: { "error": "<message>" }. A few endpoints (e.g. some file operations) may return a plain-text body rather than JSON.

application/json

401

Invalid Credentials - Your API key is invalid, missing, or disabled. Check your credentials.

Note: the 401 error body uses code, message, param, and type (there is no status field), and type is invalid_request_error.

application/json

402

Insufficient Credits - Your account or API key has run out of credits. Add more credits and retry the request.

application/json

429

Rate Limited - You have exceeded your request limits (TPM/RPM). Slow down or increase your limits.

application/json

500

Internal Error - Something went wrong on our side. Retry the request, and contact support if the issue persists.

application/json

502

Bad Gateway — failed to reach Google AI Studio.

application/json

post/v1/models/{model}:streamGenerateContent

HTTPcURLJavaScriptPython

POST /v1/models/{model}:streamGenerateContent?key=text HTTP/1.1
Host: api.fastrouter.ai
Content-Type: application/json
Accept: */*
Content-Length: 166

{
  "contents": [
    {
      "role": "user",
      "parts": [
        {
          "text": "Write a short story about a robot learning to paint."
        }
      ]
    }
  ],
  "generationConfig": {
    "temperature": 0.9,
    "maxOutputTokens": 2048
  }
}

{
  "candidates": [
    {
      "content": {
        "parts": [
          {
            "text": "text"
          }
        ],
        "role": "text"
      },
      "finishReason": "text"
    }
  ],
  "usageMetadata": {
    "promptTokenCount": 1,
    "candidatesTokenCount": 1,
    "totalTokenCount": 1,
    "cost": 1
  }
}